Green’s Dictionary of Slang

tallywag n.

the penis.

1865		‘The Dog’ in Rambler’s Flash Songster 26: The sisters soon a fancy took, and gave him sweet coresses [sic], / In return he shook his tollewag, and p----d upon their dresses.
1870		Cythera’s Hymnal 4: Three chancres did appear upon / My tolly-waggy-bus.
1870		Cythera’s Hymnal 71: Nursery Rhymes [...] There was a young princess called Dagmar, / Who said ‘I should so like to shag, Ma,’ / And says she, ‘If you speaks / To the King of the Greeks, He will lend me his own tolliewag, Ma’.
1888–94		‘Walter’ My Secret Life (1966) III 500: They stopped as they came on the man, who turning round shook his tooleywag at them.
1890–1904		Farmer & Henley Sl. and Its Analogues.