Green’s Dictionary of Slang

scotches n.

the legs.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict.
1909		J. Ware Passing Eng. of the Victorian Era 217/1: Scotch (Rhyming). Abbreviation of Scotch-pegs, the catch-rhyme for ‘leg’.
1937		J. Curtis There Ain’t No Justice 128: I want to give you a bit of strength in them scotches of yours.
1962		R. Cook Crust on its Uppers 30: Down to wearing my head in its proper place and not between my scotches like a sporran.
1974		‘P.B. Yuill’ Hazell Plays Solomon (1976) 79: I had a gander at Mrs. Gunning’s nyloned scotches.
1979		R. Barker Fletcher’s Book of Rhy. Sl. 21: Her scotches, long and slender.