⇒See the definition of become in the KJV Dictionary
(1) Greek ginomai, used in New Testament for a change of state, corresponding to Hebrew hayah of Old Testament. Compare Mt 18:3 with De 27:9.
(2) For what is fitting, suitable, proper, in New Testament: "prepei" (Mt 3:15; Eph 5:3; 1Ti 2:10); in Old Testament, na'awah, na'ah, Ps 93:5: "Holiness becometh thy house." in this sense, the adverb "becomingly" must be interpreted: "Walk becomingly toward them that are without" (1Th 4:12), i.e. in a way that is consistent with your profession.