Green’s Dictionary of Slang

(UK Und.) the lips.

1789		G. Parker Life’s Painter 167: Lips. Lispers.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1821		Flash Dict.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant II 20/1: Lispers (old cant), the lips.