Green’s Dictionary of Slang

manual labour n.

masturbation.

[c.1758		John F---g Epistle of a Reformed Rake 9: Street-walkers and Bulk-mongers sometimes take a Youth’s own Handkerchief, instead of Three-half-pence, (half-wet-half-dry) for a Manual-abortion].
2000–02		Amatory Ink 🌐.