Green’s Dictionary of Slang

a contemptuous or depreciatory term applied to men, usu. as old….

		G. Harvey Haue vvith you to Saffron-vvalden n.p.: [S]ome tall old sinckanter, or stigmaticall bearded Master of Arte.
1597		G. Harvey Trimming of Thomas Nashe E: Then thou callest them sinckanters, which is a proper Epithite vnto thy-selfe, for Sinckanter commeth of sincke and antrum a hole.
1617		S. Collins Epphata to F.T. 410: [H]e would coniure you into a boote, or into a bench-hole for your labour, like a sawcy Sinckanter, and make you an example .
1672		J. Lacy The dumb lady 63: Nib. Look, look of that old sinckanter, here's a fine mouldy gallant, an old grey badger; I must play the rogue with him.