We have motherly and fatherly. There is the city of brotherly love, and the girlfriend whose love for you is sisterly, or worse yet daughterly. According to the Collins Dictionary's trend line, sonly was in use during the 18th century, but has flatlined since, and auntly enjoyed a brief period of use in the last half of the 20th century. I suppose Uncle Sam's love for you is avuncular, but not unclely.

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    If it was in use, it was replaced by filial. There is no occurrence of it in Shakespeare, and it flat-lines against filial in Google Ngrams. If it wasn't listed in some dictionaries, I'd have said that it's a nonce word.
    – Mick
    Commented Dec 11, 2016 at 16:09
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    @ MIck Despite the etymology, "filial" refers to both daughters and sons. We do have "maternal" and "paternal.," but don't you find it strange that while we have a choice for both father and mother, when it comes to sons and uncles we are stuck with stuffy words. Both "uncle" and "avuncular" come from Latin, so it's a matter of opinion what constitutes a stuffy word, but in my opinion one of these words is stuffy and the other is not.
    – Airymouse
    Commented Dec 11, 2016 at 16:51
  • Interesting question, +1. Might this be as simple as a matter of pronunciation / phonetics? Single syllable son and aunt (not sure why this would prevent anything, though) and the more difficult to say unclely, because of the two Ls? (We can of course learn to say anything, so this probably doesn't hold much water.) Are we more averse because of how they sound?
    – Unrelated
    Commented Dec 11, 2016 at 17:12
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    Asking why is usually not productive. The answer is usually because that's the way native speakers talk. Commented Dec 11, 2016 at 18:42
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    "The answer is usually because that's the way native speakers talk. " <--- That's usually the line given by people that don't know the answer :) That line is the enemy of EL&U! Commented Dec 11, 2016 at 21:18

1 Answer 1


I'd say the most obvious difference between words like "mother," "father," "sister," "brother," and "daughter" vs. "son" and "aunt" is the stress pattern. The former group are all two-syllable words with the stress on the first syllable, so maybe there's something about that stress pattern that better accommodates an "-ly" suffix.

That hypothesis has some counterexamples, though, such as the two-syllable words "uncle" (but not *uncle-ly), "parent" (but not *parent-ly), and "sibling" (but not *sibling-ly).

So maybe it's a combination of the stress pattern and the word-final "-r". (But then you have "cousinly," which shows up in the OED a couple of times in the 19th century.) I still think that the /nl/ consonant cluster in "cousinly" is much less awkward than the potential /ntl/ cluster in "parent-ly" or /ŋl/ in "sibling-ly," not to mention the double /l/ in "uncle-ly."

So my final hypothesis, barring other counterexamples, would be a combination of stress patterns and consonant clusters.

There might also be a historical angle, though. I.e., does "parent" accept an "-ly" suffix less readily because it's a borrowing from French/Latin? (Words like "mother" and "daughter," as well as the "-ly" suffix itself, are of Germanic origin and have Germanic cognates such as "mütterlich.")

  • We can see the tendency to avoid the sequence of sounds that would be found in a word like "uncle-ly" in the way that the adverbial ending -ly usually contracts with a preceding syllabic l (we say "invisibly" and not *"invisiblely"). If I remember correctly, "sibling" only entered general usage quite recently, so that might account in part for the absence of certain derivative words.
    – herisson
    Commented Dec 31, 2016 at 21:09

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