What is the meaning of Sprat?

Any of various small, herring-like, marine fish in the genus Sprattus, in the family Clupeidae.

Any of various similar fish of other genera.

Anything petty or insignificant.

A sixpence.

To manure (land) with sprats (the fish).

sprat

floor, story/storey (level)

Source: wiktionary.org