Dad

google

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mid 16th century: perhaps imitative of a young child's first syllables da, da .

wiktionary

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From Middle English dadd, dadde, of uncertain origin.

dad (plural dads)

etymonline

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dad (n.)

"a father, papa," recorded from c. 1500, but probably much older, from child's speech, nearly universal and probably prehistoric (compare Welsh tad, Irish daid, Lithuanian tėtė, Sanskrit tatah, Czech tata, Latin tata "father," Greek tata, used by youths to their elders). Compare papa.