Green’s Dictionary of Slang

1. the penis.

1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk II 336: That which makes the genitories or generation-tools of these fair fraters so long.
1768		Gentleman’s Bottle-Companion n.p.: His generation tube he shows / Between her swelling breasts it goes.
1845		T. Rowlandson Pretty Little Games (1872) plate iv 38: His generation tube he shews. / Between her swelling breasts it goes. / His fingers to her touch hole sent, / Alas to give her small content.
1880		‘Discovery of the Longitude’ in Pearl 10 Apr. 15: ‘You, my dear;’ said he, ‘tried full many a nation, / Then say who had the longest tool of generation?’.
1888–94		‘Walter’ My Secret Life (1966) II 370: I began talking to her [...] on the subjection of generation and its working tools.
1890–1904		Farmer & Henley Sl. and Its Analogues.

2. in pl., the testicles.

1664

C. Cotton Virgil Travestie (1765) Bk IV 88: Ta’en his Knife, and in that Passion / Whipp’d off his Tools of Generation.