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Webster 1913 Edition

Adj.

Like a baby; childish; puerile; simple.

–

Ba′by-ish-ly

adv.

–

Ba′by-ish-ness

Noun.

babyish ‎(comparative more babyish, superlative most babyish)

Like a baby; childish; puerile; simple.
- 1953, C. S. Lewis, The Silver Chair, Collins, 1998, Chapter 9,
  As soon as the King and the rest of the hunting party had set off, she began making a tour of the whole castle and asking questions, but all in such an innocent, babyish way that no one could suspect her of any secret design.
For a young man, he has the most babyish voice I've heard.

like a baby