English▸ noun [in singular] the raised hairs, threads, or similar small projections on the surface of fabric or suede (used especially with reference to the direction in which they naturally lie):
carefully machine the seam, following the direction of the nap.
– ORIGIN late Middle English noppe, from Middle Dutch, Middle Low German noppe ‘nap’, noppen ‘trim the nap from’. nap2 (SENSE 2 OF THE noun) is probably from knapsack.