Green’s Dictionary of Slang

tommy tit n.

also tom-tit
[generic/assonant use of proper name tommy + SE tit, a person]

a smart young fellow.

[UK]Farquhar Recruiting Officer IV iii: There are several sorts of Toms! Tom o’ Lincoln, Tom-tit, Tom Tell-troth, Tom o’ Bedlam, and Tom Fool.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.