I noticed that the nous form of verbs always ends in -ons. For example, nous allons/allions/irons/allions/allassions/irions. However, the passé simple tense of verbs seems to always end in -mes (with the previous letter being a vowel with a circumflex).
Why is there this inconsistency? Is it because passé simple is a literary tense and "hasn't evolved" for some time? At least to me, it looks closer to Latin -mus than the other ending.
The development of the ending -ons seems to be pretty unclear. Grammaticalization: Studies in Latin and Romance Morphosyntax, by Jürgen Klausenburger (2002), describes it as "one of the most puzzling questions of Romance historical linguistics" (p. 51).
Klausenburger says that Corbett (1969) actually suggested that -ons may have come to be established in the present tense as a way of avoiding homophony with the perfect form derived from Latin -āvimus, which apparently is thought to have developed a geminate (/mm/, I guess, as in Italian cantammo) to "compensate" for the loss of -vi-, but then underwent degemination to produce a form with /m/ (p. 52).
Apparently, the imperfect and conditional 1plr forms used to end in -iens in Old French.
