"charmingly small," 1882, from itty (baby-talk form of little) and/or bitsy. Bitsy-itsy is recorded from 1875. Itty-bitty from 1849; tiddy-itty from 1852.
The fond old captain used to talk of her very much as if she were six months old, and fractions in teething, calling her his Peetums-keetums, his Pitsy-itsy-kitsy and such like, which annoyed the girl, .... ["M.B.," "John's Wife," in "Tales of the Day," 1861]
updated on October 27, 2017