Middle English proselite, from Anglo-French prosilite, from Late Latin proselytus proselyte, alien resident, from Greek prosēlytos, from pros near + -ēlytos (akin to ēlythe he went) — more at pros-, elastic First Known Use Noun 14th century, in the meaning defined above Verb 1624...
word-forming element in words of Greek origin meaning "to, toward, before," from Greekpros(prep., adv.), alsoproti, "from, forth, from (one point) toward (another); furthermore; in the face of," from PIE *proti-(source also of Sanskritprati"to, against")....
" noun use of adjective meaning "having arrived," from second aorist stem ofproserkhesthai"to come or go; surrender; associate with," fromproti"toward" + root ofeleusesthai"to be going to come," from PIE*elu-to-, from root*leudh-"to go." Originally in English "a Gentile converted...