Many French words have lost etymological /l/. I have read that this occured due to a process of l-vocalization around the 10th-12th centuries which turned pre-consonantal l to u after any vowel aside from i (Manz). It seems that in general, el developed to the triphthong eau (which in Modern French has become /o/) as in beau < bellus, chateau < castellum, couteau < cultellus, veau < vitellus. The use of -eau instead of -el in the singular of words like this is said to be a back-formation from plural forms ending in -eaus/-eaux (Manz, Ricard).

However, in some cases, el apparently became the diphthong eu (Modern French /ø/).

It looks to me like eu might have been conditioned by a preceding glide /j/:

  • vieux < Latin vetulus
  • pieu < OF pels < Latin palus
  • cayeu/caïeu < Latin catellus

However, it's also present in the word cheveu(x) "hair(s)," from Latin capillus. At first, I wondered if it might relate to the etymological vowel quality, since from what I understand Latin /i/ corresponds to Proto-Romance /e/, which was distinguished from /ɛ/ in stressed syllables. But the word sceau is from Latin sigillum, and it still has eau, so I'm not sure if that's relevant.

I'd appreciate any explanation of how cheveu(x) developed phonetically. Perhaps the use of eu instead of eau here just reflects earlier or dialectal variation that was mostly leveled out in standard French, but that in itself would be an interesting answer.


  • Have you considered it could be a special case due to the possible interference with “horse(s)” cheval/chevaux < Gaulish / Late Latin caballus which was likely an important word until only very recently. – Stéphane Gimenez Aug 30 '16 at 9:41
  • @StéphaneGimenez: Hmm. I wondered a little bit, but I wasn't sure how likely that was, since from what I understand sound changes aren't normally inhibited by possible homophony (at least, not unless the potential homophones would be very confusable, which doesn't seem like it would be the case with "horse" and "hair"). – sumelic Aug 30 '16 at 10:40
L /kasˈtɛl.lʊm/ > VL /kasˈtɛl.lũ/ > OF /t͡ʃahˈtɛl/ > MF   /ʃaˈtɛau/> F /ʃaˈto/
L /ˈwɛ.tʊ.lʊm/  > VL /ˈβɛ.lũ/ > /ˈvjɛ.lu/ > OF /vjɛl/ > MF /vjɛu/ > F   /vjø/
L /kaˈpɪl.lʊm/  > VL /kaˈβel.lũ/  > OF /t͡ʃəˈvel/  > MF   /ʃəˈvɛu/ > F /ʃəˈvø/
L /sɪˈɡɪl.lʊm/  > VL /se.ɣɛl.lũ/  > OF /səˈɛl/    > MF     /sɛau/ > F    /so/

L - Latin, VL - Vulgar Latin, OF - Old French, MF - Middle French, F - French

I apologize for my formatting. It is hard to do this in a neat style.

If I had included every step, the 4 sound change chains above would take a whole page.

In words

This wikipedia page has detailed the causes quite well.


  • Closed /ɛl/ becomes /o/.
  • Late-closed /ɛl/ becomes /jɛl/ (because of vowel-breaking /ɛ/ > /jɛ/) > /jø/.
  • /el/ becomes /ø/.

Late-closed refers to those that are open in Vulgar Latin and then became close, in terms of the syllable (not the vowel). Usually they only have one l, so the syllable was open until the final vowel was lost, causing l to be shifted to the now final syllable (second chain, /ˈvjɛ.lu/ > OF /vjɛl/).

capillum > cheveux

Short i /ɪ/ in Latin becomes /e/ in Vulgar Latin.

Only long i /iː/ is preserved as /i/ in Vulgar Latin (the lengthening is basically gone).

For example, L /ɡenˈtiː.lem/ > VL /genˈti.lẽ/ > F /ʒɑ̃ˈti(j)/.

Therefore, the answer to your question is, quoting you:

Latin /i/ corresponds to Proto-Romance /e/, which was distinguished from /ɛ/ in stressed syllables.

sigillum > sceau ?

This is a strange case. The "eau" can only be explained by that the /i/ has shifted to /ɛ/ in VL.

This word is even stranger. In almost all descendants that kept the "g", the first vowel is "u" instead of "i" (e.g. Italian "suggello"), for which I have two explanations:

  1. That the first sound has become the sonus medius.

  2. That it is a regularization of "sigillum" based on the prefix "sub-" ("sug-" before another "g"). It may have been entirely analogically constructed from "suggetto" (which can also explain /i/ > /e/). But, this is irrelevant to the French word "sceau" (since the French word is "sujet").

(work in progress)


I am far from an expert at this. Please do notify me if I made any mistake.


(this is meant to be a comment but it's too long so I posted it as an answer.)

Zink (1986/2013) in his "Phonétique historique du français" gives the following reconstruction - I preserved his notation:


IIIe s. ẹ

IV2 kabẹllus

Ve s. k̬aβ


VIIe s. tšẹvẹɫs

XIe s. tševeus

XII1 œ́us

-2 œ́s

XIIIe s. ševœ́(s) (afr. cheveus)

  • Where is the schwa? – Kenny Lau Aug 30 '16 at 17:59
  • In IPA: /kaˈpɪl.lʊs/ > /kaˈbel.lʊs/ (III) > /kaˈβel.lʊs/ (IV) > /kʲaˈβel.lʊs/ (V) > /t͡ʃeˈvel.los/ (V) > /t͡ʃeˈveɫs/ (VII) > /t͡ʃEˈvEus/ (XI) > /t͡ʃEˈvøus/ (XII) > /t͡ʃEˈvøs/ (XII) > /ʃEˈvø(s)/ (XIII) – Kenny Lau Aug 30 '16 at 18:01

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