EtymOnline is an excellent resource for online etymology searches. If, however, I am looking for lists of words sharing a given Latin, Greek or other root (which I call "reverse etymology"), I do not know which tool I could use. Do you know any?

The only thing I could think of is, if I had access to an offline etymology dictionary, I could then perform a full-text search into its content.


This can be achieved with a touch of Google-fu.

We want to limit our Google search to search only the site, http://www.etymonline.com/.

From reading the url structure of each result, we notice that definitions all contain ?term=, so can we refine the search with these bits of info:

site:etymonline.com inurl:term

Then, we add a space and the term we are looking for; if it appears in the text describing a word's etymology, we have a hit.

For example, we'd type the following if we wanted to search for phagos:

site:etymonline.com inurl:term phagos

Search results for "phagos"

We are a touch limited in that we must rely on the definitions containing that particular variant. For example, the above search returns 5 hits; however, a search for phagous returns 13 hits despite phagos and phagous sharing a common root.

Hope that helps!

EDIT: I've further played with this and noticed that occasionally it returns search pages which don't really add much.

These can be filtered out as they all contain the expression ?search=, so we can use:

site:etymonline.com inurl:term -inurl:search phagos

For anyone interested in understanding how that works, prepending a - negates the statement so -inurl:search evaluates to AND url does not contain "search".

  • That's a great approach. I just tried it with hydro and phobia and it worked very well! – b.roth Apr 7 '11 at 15:19

Wiktionary maintains descendant lists, but they are far from complete. See e.g.:


Not online, but I picked up a second-hand copy of Pokorný's Indo-European Dictionary some years ago, and I often refer to it for this. I'm sure that scholarship has moved on since, though.

  • +1 for Pokorny! It is also available online on a website by the university of Leiden. It uses a phonetic rendering in Latin letters and characters whose name I forgot and that I can't properly read—or at least as they are displayed in my browser. ieed.nl/%5Cindex2.html It also has Frisk's Greek etymological dictionary! And here is a link to the list of PIE roots in Pokorny: homepage.ntlworld.com/richard.wordingham/pok/pok_index.htm – Cerberus Apr 8 '11 at 4:45
  • P.S. Are you sure we need the accent on the y? Wikipedia doesn't have it, nor does Leiden. en.wikipedia.org/wiki/Julius_Pokorny – Cerberus Apr 8 '11 at 4:48
  • Thanks for the Leiden link: I didn't know that was all available. As for Pokorný - it looks as if he dropped the accent - it exists on the name in Czech (See en.wikipedia.org/wiki/Pokorn%C3%BD). But I wonder where I got it from then? – Colin Fine Apr 8 '11 at 13:48
  • Yeah he must have dropped it then, no other explanation I can think of. I see I forgot to upvote you in my haste to add an extra comment, how silly. Here it is. – Cerberus Apr 8 '11 at 14:07
  • I was sure I must have got the "ý" from somewhere, but I've been to check the printed copy and it has "y". I never even questioned the "ý" when I wrote the comment. – Colin Fine Apr 11 '11 at 11:05

The American Heritage Dictionary (used to be online, no more) had great etymology links back to the root of a word, which then had a link to all the words derived from the root. (so you could go backward and forwards in time).

Those old pages are available through the 'wayback machine' at


AHD (at that archive site) also has accompanying articles for Indo-European and Semitic roots, and lists of those roots which then link forward to derivatives:


Seems to be slow, but likely to be exactly what you want.

(A comment points out that the dictionary is still online, but it just doesn't offer the same list of IE roots or clickable etymology.)

  • FYI, you can still access the American Heritage Dictionary on [Yahoo! Education] (education.yahoo.com/reference/dictionary) or via Yahoo! Search by typing define word (replace 'word' with what you want). Etymology links not clickable though. – Ankur Banerjee Apr 7 '11 at 16:44
  • +1 For these, I use them all the time as well. – Cerberus Apr 8 '11 at 4:35


As above, currently the roots are hotlines as well. Basically, you can search on a root word or particle and it shows all of the modern words derived from that root. Try searching for *per- in the search box.

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