Inchoative verb-forming suffix
From Latin -escere, -iscere, and -ascere 'id.,' depending on the vowel stem.
From Proto-Italic *-sk-e/o- 'id.' From Proto-Indo-European *-sḱ-e/o- 'id.'
Western Vulgar Latin: Asturian -ecer, Portuguese -ecer, -escer, Catalan -eix, French -is, Italian -isco; Eastern Vulgar Latin: Aromanian -esc
Celtic: Old Irish -c; Balto-Slavic: Lithuanian *-šý- (< prašýti), Old Church Slavonic *-si- (< prositi); Germanic: Gothic *-h- (< fraihnen); Armenian: *-c'a-; Indo-Iranian: Sanskrit *-ch- (> pr̥chā́mi "to ask"), Avestan *-sa (> pərəsa "to ask"); Anatolian: Hittite *-iski indicating repeated action
"The productive descendants of [Proto-Indo-European *-sḱ-é/ó-] differ in meaning from branch to branch. In Anatolian, the suffix indicates repeated, habitual, or background action, or action applied to more than one object... The habitual or durative sense is also found in Homeric Greek... Other Latin verbs with the suffix, however, are inchoatives (indicating the beginning or inception of an action or state)... Several verbs having the suffix that are reconstructible for PIE refer to asking or wishing, indicating perhaps that the suffix also once had a desiderative function." ~ B. Fortson, Indo-European Language and Culture (2011)