Green’s Dictionary of Slang

catso n.

[Ital. cazzo, the penis, lit. ‘thrust’; it is possible, comparing similar fig. use of penis = fool usages, plus catso! excl., that sense 2 in fact predates sense 1]

1. [late 16C–early 17C] a rogue or rascal.

2. [17C+] (also cadzo, carts, cartso, cartsue, catzo, cazzo) the penis.

3. in fig. use of sense 2, courage.

In compounds

cartsue case (n.)

[mid–19C] (UK Und.) the vagina.