Green’s Dictionary of Slang

an excl. aimed at any passing red-headed man.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Hyp, or Hip. A mode of calling to one passing by. Hip, Michael, your head’s on fire; a piece of vulgar wit to a red haired man.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.