Green’s Dictionary of Slang

usu. in pl., the testicles.

1788		‘The Gobbio’ Chap Book Songs 6: She spyed a Piper peeping out, / Between two little drummers he lay.
1831		Satirist (London) 31 July 134/1: [T]he song commencing ‘When the merry drummer beats to bed, / Then the little fifer hangs his head, / Still and mute—’ we cannot precisely understand.