morgan rattler, n. — Green’s Dictionary of Slang

morgan rattler n.

[the term exists in a popular fiddle tune but ety. unknown and ? anecdotal; unlike the rigid police truncheon, it was made of a flexible material; the EDD defines it as 1. ‘a hard and reckless fighter’, 2. the weighted cane or stick, 3. ‘anything good or striking of its kind’]

1. a penis.

c.1790

‘Morgan Rattler’ in Chap Book Songs 3: At night with the girls he still is a flatterer, / They never seem coy, but tremble for joy, / When they get a taste of his Morgan Rattler.

2. a weighted stick used as a weapon, with a knob of lead at one or both ends, often used by garrotters.

1937–84

Partridge DSUE (1984) 752: [...] low s. (—1902) ex dial. (—1886); † by 1910.