Green’s Dictionary of Slang

1. (UK Und.) a cow.

1674		Head Canting Academy (2nd edn).
1688		J. Shirley Triumph of Wit 214: A Cow Mower.
c.1698		B.E. Dict. Canting Crew n.p.: Mower A Cow.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1754		Scoundrel’s Dict. 16: A Sow [Cow] – Mower.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1848		Flash Dict. in Sinks of London Laid Open.

2. in fig. use, describing a person.

1852

A. Smith Comic Tales 40: Alas! the hoary old mower generally takes it into his head to act in precisely an opposite manner.