• Who, Quis
  • What, Quid
  • When, Quando
  • Where, Quo
  • How, Quomodo
  • Why, Cur

There's one exception on each side, but otherwise this pattern is pretty consistent. Is there a linguistic or etymological reason for this?

  • 49
    Because they all come from the Proto-Indo-European root *kʷo-, the stem for relative and interrogative pronouns. Latin retains the original labiovelar stop, while English and other Germanic languages has had it changed by the processes called "Grimm's Law" into a labiovelar fricative /hw/, pronounced simply as /w/ by many speakers. Commented Jan 4, 2017 at 22:08
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    @JohnLawler and that's not an answer because ...?
    – bib
    Commented Jan 5, 2017 at 0:29
  • 2
    @KevinKeane: you are muddying the waters! This is definitely not a case of convergent evolution (even allowing that such a thing exists for languages).
    – TonyK
    Commented Jan 5, 2017 at 16:30
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    @sgroves I think John Lawler's comment is excellent (as do many others), and comments are not permanent on this site. It could disappear and that insight lost. My comment was meant to be an encouragement to transform his comment into an answer so we all can continue to benefit from it. I have no better answer, and merely copying John's comment into an answer posting of my own would not be right.
    – bib
    Commented Jan 6, 2017 at 19:34
  • 3
    @bib I think the appropriate course of action if John doesn't make an answer would be to make a community wiki answer with his comment in it
    – Sparr
    Commented Jan 7, 2017 at 0:33

4 Answers 4


Both sets of words come from a Proto-Indo-European root *kʷ(o)- that probably marked an interrogative pronoun. In the Germanic languages, Grimm's Law spirantized this *kʷ into /xw/ or /hw/, which later merged with /w/ in many Germanic languages (Dutch wat, German was, Swedish vad, etc.), though not all: English has what (in some dialects still pronounced with and unvoiced /ʍ/), Icelandic has hvað /kvað ~ xvað/, and Norwegian is probably the silliest, having dialectal and lexical variation between /v ~ kv ~ k ~ Ø/ (the last only before back vowels).

In Latin, *kʷ remained in most words as /kw/ (written ⟨qu⟩), so we have quis, quod, quam, etc. from this root. Cūr is from the same root, but before a high back vowel /u/ the labial element in /kw/ was usually lost in Latin, so early Latin quōr /kwoːr/ (which regularly became quūr /kwuːr/) yielded cūr /kuːr/. Even where Latin kept the labial element in /kw/, though, it usually (though not always) disappeared in the Romance languages, the daughter languages of Latin, leaving just a /k/ as in Spanish que, Italian che, French quand, etc.


In the other branches of Indo-European languages, the development was generally as follows:

Greek: in the largest dialect group, Ionic-Attic, PIE /kʷ/ (mostly) became /t/ before front vowels (τίς tis ‘who’, τί ti ‘what’) and /p/ elsewhere (ποῦ ‘where’). In some other dialects, it (at least sometimes) turned into /k/.

Balto-Slavic: In Slavic it generally resulted in /k/ before back vowels and č /tʃ/ before front vowels (Old Church Slavonic čьto ‘what’, kъto ‘who’); in Baltic generally /k/ everywhere (cf. Lithuanian kas ‘who, what’).

Celtic: It became /k/ in Goidelic (Old Irish cia ‘who’, cid ‘what’) and /p/ in Brythonic and Continental Celtic (Old Welsh pwy ‘who’, pa ‘what’).

Indo-Iranian: In Sanskrit it was mostly generalised to /k/ (कः kaḥ ‘who’, किम kim ‘what’), though it should have yielded /c/ before front vowels; in Iranian there was no such generalisation, and it generally became /k/ before back vowels and /tʃ/ before front vowels (Avestan ‘who’, čim ‘what’)

Others: In Hittite and Tocharian, it remained /kʷ/ (Tocharian kus, kᵤse /kʷse/ ‘who’, Hittite kui-/kue-/kuu̯a- /kʷi-, kʷe-, kʷa-/). In Armenian it seems to have been irregularly weakened to /h/, which was subsequently lost: the generalized stem հի- hi- became ի- i-, found in words like ինչկ inč’ ‘what’.

[From StoneyB's comment:] Scots English employed /xw/ at least into the 16th century—and spelled it ‹quh›. See this question.

  • 3
    And: in Slavic it generally resulted in č /tʃ/ (or similar); in Baltic generally /k/; in Goidelic, /k/; in Brythonic and Continental Celtic /p/; in Sanskrit mostly generalised to /k/; in Iranian /k/ and /tʃ/ after back and front vowels respectively; in Hittite and Tocharian, it remained /kʷ/… and I'm too tired to think of more off the top of my head right now. Commented Jan 4, 2017 at 22:21
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    Actually, the pronounced "h" is still naturally (without revival) widespread in the USA South as well as North of England and Scotland. This in turn respawns it in the wider language: a great many primary school children here (Australia) pronounce the "h" because they find it easier to learn the spelling of "wh-" pronouns: teachers often make a point of pronouncing it like this when teaching the spelling and I think they like the somewhat unwonted (to some people's ears) sound to play around with. There are also enough people around of Scottish / USA background that children hear it .... Commented Jan 5, 2017 at 1:24
  • 1
    @StoneyB Not really. Chaucer re-introduced great swathes of Anglo-Saxon words into his writings such that some of the commonest words today were revived by him ("lufu" became "love" and many others), living today after having spent a couple of centuries in stasis. Also, there can be a natural tendency to differentiate homophones to clarify meaning, so this could also explain a "revival" in some cases. Commented Jan 5, 2017 at 1:33
  • 1
    @WetSavannaAnimalakaRodVance O yah, /hw/ is standard in my own dialect (East Alabama). As for the 'reintroduction', I'm not talking about Norwegian lexicon, but Norwegian morphology--they're reviving abandoned inflectional endings! ... I think you're exaggerating Chaucer's "revivalism" -- he was extending the influence of a living language, not reviving a dead one. MED, for instance, has scores of instances of love (in various spellings!) from the 200 years after the last entries in the Anglo-Saxon Chronicle. Commented Jan 5, 2017 at 3:03
  • 1
    @Luaan Czech "jak" cognates with Panslavic "kak/kako", deriving ultimately from PIE *kʷ(o)-. The first part of "jak" comes from "jaký" (what/which), cognating with Lithuanian "jóks" ('any', see also "kóks", "tóks"), deriving from some other PIE root. "proč" got formed by contracting "pro co" ("for what"), akin in meaning to "pourquoi" or "wherefore".
    – IS4
    Commented Jan 6, 2017 at 13:27

More specifically, you are seeing part of the sound change *kʷ > hw [xʷ] in Grimm's Law. Grimm's Law is a well known group of ancient sound shifts that affect all of the Germanic languages (not just English) and differentiate them from the Romance and Celtic languages that did not undergo the change. In fact, it can be argued that Grimm's Law defines the Germanic language family.

Grimm's law is also why English (Germanic) foot maps to French (Romance) pied and Latin pedis. The Proto-Italo-Celto-Germanic word underwent two consonant changes to become the Germanic form - the "p" morphed to "f" and the "d" morphed to "t".

Also, note that post-Grimm's law borrowings from Latin and French into English have resulted in pairings of related words, one of which displays Grimm's law (and is the native English word) and one of which does not. Examples are hound and canine, hunt and capture, tooth and dental, and hundred and century.

  • 2
    What about the vowel shift that you see in pied / pedis to foot? Commented Jan 5, 2017 at 5:51
  • 1
    @Cody Gray: New question = new question. Grimm’s law is only one of many sound laws (not all of them well understood) that describe the evolution from PIE to English on the one hand, and to Latin on the other hand.
    – chirlu
    Commented Jan 5, 2017 at 12:19
  • 2
    BTW, the nominative form of the Latin word for foot is pes, while pedis is the genitive. (The French form derives from the Latin accusative, which is pedem.)
    – chirlu
    Commented Jan 5, 2017 at 12:21
  • 2
    Also, note that post-Grimm's law borrowings from Latin and French into English have resulted in pairings of related words, one of which displays Grimm's law (and is the native English word) and one of which does not. Examples are hound and canine, hunt and capture, tooth and dental, and hundred and century. Commented Jan 5, 2017 at 14:18

To add to Cerberus's excellent answer that all the words have the same Indic root, one can still see English language inscriptions in Scotland where the said wh- words are written qu-. I can only cite personal observation in several churches in Edinburgh and I don't know whether this practice arose from a natural orthography, from a Scottish wish to differentiate oneself from the English, or from a wish to reaffirm Scottish-French solidarity (several of the examples, if I recall correctly, were from the time of Mary Queen of Scots).


Great replies! I once took a course on Celtic languages and learned that there was a division between "p-Celtic" and "q-Celtic". I mention these terms here, as I haven't seen them in the posting above (they might not be official terms though).

A clear example: in English we have father, in Swedish we have far, in German we have Fater (I think), in French we have père, and in Latin we have pater.

I guess this is what is referred to as Grimm's Law above.

  • 5
    It's Vater, not Fater for German.
    – Glorfindel
    Commented Jan 6, 2017 at 14:47
  • 4
    Pronounced that way though. Commented Jan 6, 2017 at 16:59
  • 1
    Grimm's Law refers specifically to the sound change that gives us "f" in Germanic languages like English, Swedish and German. The other types of sound changes in language groups like p-Celtic have different names, or sometimes no special names at all.
    – herisson
    Commented Jan 7, 2017 at 2:24
  • The terms p-Celtic and q-Celtic are not generally used by linguists anymore. It was once thought that those were the two main branches of Celtic, divided on the basis of what /kʷ/ became (/q = kʷ/ in q-Celtic, /p/ in p-Celtic). But there is wide consensus nowadays that this split is fairly incidental. The split between the Continental (Gaulish, Lepontic, Celtiberian, Galatian, etc.) and Insular (Irish, Scottish, Welsh, Cornish, Breton) Celtic languages was almost certainly the main ‘splitter’. The loss of /kʷ/ in all these languages happened later: first in Continental Celtic (generally → Commented Jan 7, 2017 at 11:24
  • → becoming /p/), then in the Brythonic branch of Insular Celtic (Welsh, Cornish, Breton—becoming /p/ as well), and finally in the Goidelic branch of Insular Celtic (Irish, Scottish—becoming /k/). This is similar to how, within the Italic branch of IE languages, Latin has retained /kʷ/, written ⟨qu⟩, while in Oscan and Umbrian it changed to /p/. You could also speak of ‘p-Italic’ and ‘q-Italic’ if you wanted; but no one does. The term only stuck for Celtic. Commented Jan 7, 2017 at 11:25

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