proselyte
One who has converted to a religion or doctrine, especially a gentile converted to Judaism.
Woe unto you, scribes and Pharisees, hypocrites! for ye compass sea and land to make one proselyte, and when he is made, ye make him twofold more the child of hell than yourselves.
Where it comes from
From Old French proselite, from Late Latin proselytus (“proselyte, alien resident”), from Ancient Greek προσήλυτος (prosḗlutos, “newcomer, convert”) (from πρός (prós, “to, towards”) and the stem -ηλυ- of ἐλήλυθα (elḗlutha), perfect of ἔρχομαι (érkhomai, “come”)), translation of Hebrew גר (ger) in the Septuagint translation of the Torah (e.g., Exodus 12:49); also used in Matthew 23:15, Acts 2:10, Acts 6:5.
Adapted from the Wiktionary entry proselyte (CC BY-SA 4.0).