Meaning

noun an informal term for a father; probably derived from baby talk

originFrom Early Modern English dadd, dadde (circa 1500), undoubtedly older, from unrecorded Middle English *dadde, of uncertain ultimate origin. Compare West Frisian deite (“dad, daddy”), Swabian Dede (“Godfather”). * Perhaps of Celtic origin, compare Welsh and Breton tad (from Proto-Brythonic *tad), Old Irish data; and possibly related to Russian дя́дя (djádja, “uncle”) and/or Russian де́душка…

Etymology from Wiktionary, CC BY-SA 3.0