Preach
Middle English: from Old French prechier, from Latin praedicare ‘proclaim’, in ecclesiastical Latin‘preach’, from prae ‘before’ + dicare ‘declare’.
wiktionary
From Middle English prechen, from Old French prëechier, precchier (Modern French prêcher), from Latin praedicō. Doublet of predicate.
The Latin word is also the source of Old English predician(“to preach”), Saterland Frisian preetje(“to preach”), West Frisian preekje(“to preach”), Dutch preken(“to preach”), German Low German preken(“to preach”), German predigen(“to preach”), Danish prædike(“to preach”), Swedish predika(“to preach”), Icelandic prédika(“to preach”), Norwegian Nynorsk preika(“to preach”).
etymonline
preach (v.)
Middle English prechen, "deliver a sermon, proclaim the Gospel," from late Old English predician, a loan word from Church Latin; reborrowed 12c. as preachen, from Old French preechier "to preach, give a sermon" (11c., Modern French précher), from Late Latin praedicare "to proclaim publicly, announce" (in Medieval Latin "to preach," source also of Spanish predicar), from Latin prae "before" (from PIE root *per- (1) "forward," hence "in front of, before") + dicare "to proclaim, to say" (from PIE root *deik- "to show," also "pronounce solemnly," and see diction). Related: Preached; preaching.
Meaning "give earnest advice, especially on moral subjects" is by 1520s. To preach to the converted is recorded from 1867 (the form preach to the choir attested from 1979).
