Christen
Old English crīstnian ‘make Christian’, from crīsten ‘Christian’, from Latin Christianus, from Christus ‘Christ’.
wiktionary
From Middle English cristenen, cristnien, from Old English cristnian(“to christen, baptise”), from cristen(“ Christen, Christian”) + -nian. Cognate with Dutch kerstenen(“to christen”), Middle Low German kristenen, kerstenen, karstenen(“to christen”), Danish kristne(“to christen”)Swedish kristna(“to christen”), Icelandic kristna(“to christen”).
etymonline
christen (v.)
c. 1200, "to baptize into the Christian church," from Old English cristnian "to baptize," literally "to make Christian," from cristen "Christian" (see Christian). Especially to baptize and name as an infant, hence "give a name to at baptism" (mid-15c.) and the general sense of "give a name to" anything, without reference to baptism (1530s). Related: Christened; christening.