From Middle Dutch fijnkens, from fijn ("fine").

finikin

1. (dated) Excessively dainty or fastidious.
   • 1847 January – 1848 July, William Makepeace Thackeray, chapter 3, in Vanity Fair […], London: Bradbury and Evans […], published 1848, →OCLC ↗:

     The bearded creatures are quite as eager for praise, quite as finikin over their toilettes, quite as proud of their personal advantages, quite as conscious of their powers of fascination, as any coquette in the world.

finikin (plural finikins)

1. Alternative form of finnikin