Origin and history of -kin

diminutive suffix, first attested late 12c. in proper names adopted from Flanders and Holland. As it is not found in Old English it probably is from Middle Dutch -kin, properly a double-diminutive, from -k + -in. Equivalent to German -chen. Also borrowed in Old French as -quin, where it usually has a bad sense.

This suffix, which is almost barren in French, has been more largely developed in the Picard patois, which uses it for new forms, such as verquin, a shabby little glass ( verre); painequin, a bad little loaf ( pain); Pierrequin poor little Pierre, &c. ["An Etymological Dictionary of the French Language," transl. G.W. Kitchin, Oxford, 1878]

Used in later Middle English with common nouns. In some words it is directly from Dutch or Flemish.