Green’s Dictionary of Slang

hatter n.2

see brown-hatter n.

In phrases

who’s your hatter?

catchphrase .

[UK]Leicester Jrnl 1 Mar. 4/1: Men's garments must topsy-turvy whirl’d, / And alter’d every fortnight — Who’s your hatter?
[UK]Sportsman 20 Oct. 2/1: Notes on News [...] ‘Who’s your hatter?’ a common bit of street chaff, originated [...] in the fact the the eminent hatter Mr Harris, some time M.P. for Souths ark, presenting each of his supporters with hat, which the other side laughingly asked them the above obnoxious question their going to poll.