means a single loop of thread made by a needle in sewing, knitting, or surgery — or, loosely, a sharp pain in the side from exertion

from From Old English 'stice,' meaning a prick or sting — the sharp jab of a needle going through cloth. It's a cousin of 'stick' (the verb), both rooted in a Proto-Germanic word for piercing. The fabric sense and the painful 'stitch in the side' both trace back to that original idea of being stuck or pierced — sewing tamed the sting into something useful.