I'm writing in English, the lingua franca for linguistics terms? Anyhow, I'm assuming that some book or paper will expound this:

Etymology [moisir - Wiktionary]

From Vulgar Latin *mŭcēre, from Latin mūcēre, from mūcus.
For the regular phonetic evolution of [Latin] -ēre > [French] -ir after palatal -c-, see also gésir, loisir, plaisir.

  • A lingua franca aims at making things simpler but involves in itself an added complexity, why complicate things by establishing several such means of simplification that will each increase this supplementary task?
    – LPH
    Commented Jul 23, 2019 at 4:12

1 Answer 1


I'm not aware of a recent paper that develops the phenomenon, but most manuals of Old French or about the phonetic development of French from Latin will have a paragraph on this (for example, J.-M. PIERRET, Phonétique historique du français et notions de phonétique générale, p. 198; P. BOYD-BOWMAN, From Latin to Romance in Sound Charts, pp 32-35; or even Wikipedia)

The root mechanism at work here is that the sequence /jej/ or /ɪ̯eɪ̯/ in Old French contracted to /i/ around the 10th century. This happened whatever the source of the yods, be it inherited from Latin (1), a diphthong (1, 2, 3, 4), a lenited consonant (2), a palatal offglide after a palatalised consonant (2, 4) or a palatal offglide ejected from a posttonic syllable (1, 3):

  1. Peior /'pej.jor/ -> vulgar */'pɛ.jɔr/ -> pre-French */'pɛj.rɔ/ (metathesis of ɔr then ejection of yod to the preceding syllable) -> OF /'pɪ̯ej.rə/ (diphthongisation of the once open /ɛ/ to /ɪ̯e/ -> /'pi.rə/ pire

  2. cacat /'ka.kat/ -> pre-French */'kʲɛ.ɣaθ/ -> OF /t͡ʃʲe.jə(θ)/ -> /t͡ʃi.ə/ chie

  3. Decem /ˈde.kem/ -> vulgar */'dɛ.kʲɛ/ -> pre-French */dɛj.t͡sɛ/ -> OF /dɪ̯ejt͡s/ -> /dit͡s/ dix

  4. Cēram /'keː.ram/ -> vulgar */kʲe.ra/ -> OF /'t͡sʲeɪ̯.rə/ -> /'t͡si.rə/ cire

This is what happened to the infinitive suffix -ēre after /k/. /k/ was palatalised by /e/ to /t͡sʲ/ while the open syllable /e/ diphthongised to /eɪ̯/. Normally, /t͡sʲ/ would have evolved to /z/ and /eɪ̯/ to /wa/, but next to each other they formed a /jej/ sequence which reduced to /i/.

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