Green’s Dictionary of Slang

cinquanter n.¹

a gambler.

1596		Nashe Saffron Walden 7: Some tall old cinquanter or stigmatical-bearded Master of Arts.
1597		The trimming of Thomas Nashe Gentleman n.p.: [T]hou callest them sinckanters, which is a proper Epithite vnto thy selfe, for Sinckanter commeth of sincke and antrum a hole, and as all the puddle and filth in the channell, still runnes all a long till it comes to a hole or antrum.
1617		Collins Defence Bishop Ely ii x 410: He would coniure you into a boote, or into a bench-hole for your labour, like a sawcy Sinckanter [OED].
a.1640		T. Jackson Works 3058: One Volanerius an old Sinkanter, or Gamester and Scurrilous Companion by profession .
1672		J. Lacy The Dumb Lady 63: Look, look of that old sinckanter, here's a fine mouldy gallant, an old grey badger; I must play the rogue with him, though I suffer for it.