looking glass, n.¹ — Green’s Dictionary of Slang

looking glass n.¹

[one’s reflection in the urine, as well, poss., as the attention paid by contemporary physicians to the urine itself. Thus the 18C riddle: ‘Q. Why is a Chamber-Pot call’d a Looking-Glass? A. Because many rarely see their Faces in any other’]

a chamberpot.

1613		Middleton Chaste Maid in Cheapside III ii: A looking glass; they have drunk so hard in plate, That some of them had need of other vessels.
c.1698		B.E. Dict. Canting Crew n.p.: Looking-glass a Chamber-Pot.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1800		Sporting Mag. Sept. XVI 284/1: Two blades [...] / Bid John, when both were half-seas-o’er, / To bring a looking-glass / [...] / A glass! beshrew your empty sconce! / We want a chamber-pot.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.

looking glass n.1

looking glass n.¹