Swatch
early 16th century (originally Scots and northern English, denoting the counterfoil of a tally, and later a tally fixed to a piece of cloth before dyeing): of unknown origin.
wiktionary
From earlier Northern England dialectal swache(“the counterfoil or counterstock of a tally”) (1512); further etymology unknown. Cognate with Scots swach, swatch. Compare English swath, swathe. Compare also Old English swæcc(“taste; flavour; odour; fragrance”).
Origin unknown; originally used chiefly in the East of England.
etymonline
swatch (n.)
1510s, "the countercheck of a tally" (Northumberland dialect), later "a tally attached to cloth sent to be dyed" (1610s, in Yorkshire), of unknown origin. Century Dictionary compares swath. Meaning "a sample piece of cloth" is from 1640s.