Green’s Dictionary of Slang

twiddle-diddles n.

the testicles.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Twiddle Diddles Testicles.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.