Green’s Dictionary of Slang

1. a fool, a jester [SE hobby horse, the performer, in a morris dance, who manipulates, with much capering, the wicker horse that is part of the trad. ‘cast’].

1599		Shakespeare Much Ado About Nothing III ii: I have studied eight or nine wise words to speak to you, which these hobby-horses must not hear.
1608		Dekker Honest Whore Pt 2 (1630) III iii: De fooles cap dere, and de cloutes; heare? doest thou make a Hobby-horse of me?
1611		J. Cook Greenes Tu Quoque Scene xvi: The tother Hobby-horse, I perceive is not forgotten.
1633		Ford ’Tis Pity She’s a Whore I iii: bergetto: Why, uncle, should I sit at home still, and not go abroad to see fashions like other gallants? donaldo: To see hobby-horses!
1639		J. Taylor Crabtree Lectures 66: Thou a Horse-leich? thou an Hobby-horse.
1672		J. Phillips Maronides (1678) 140: And Jupiter’s a Hobby-horse, / he does not kick her out of doors.

2. (also she-hobby) a prostitute, a promiscuous woman; a mistress [SE hobby horse, a small horse; she can be ‘ridden’ by all and sundry].

c.1595		Shakespeare Love’s Labour’s Lost III i: arm.: Callest thou my love ‘hobby-horse?’ moth.: No, master; the hobby-horse is but a colt, and your love, perhaps a hackney.
1602		Middleton Blurt, Master Constable G2: As for the light Hobby-horse my Sister, whose foule name, I will raise out with my Poniard.
1627		G. Peele Merrie Conceited Jests 17: My she-hobby was very dainty.
1639		J. Shirley Gentleman of Venice V ii: Thou dull islander! ’Cause you can dance, and vault upon a hobby-horse, Do you think to mount madonas here, and not Pay for the sweet career?
1759–67		Sterne Tristram Shandy (1949) 139: I need not tell the reader, if he keeps a hobby-horse, – that a man’s hobby-horse is as tender a part as he has about him.
1791		Essay on the Art of Strangling 7: Mounting men, unaccustomed to hard riding, upon those gentle and ambling pacers, the most pleasant and delightful of all possible hobby-horses, urge them to drive on at so unconscionable a rate.