late 14c., "to make a plan or diagram," from Old French trasser "delineate, score, trace, follow, pursue" (12c.), from Vulgar Latin *tractiare "delineate, score, trace" (cf. Spanish trazar "to trace, devise, plan out," Italian tracciare "to follow by foot"), from Latin tractus "track, course," literally "a drawing out," from past participle stem of trahere "to pull, draw" (see tract (n.1)).
Meaning "to pass over" (a path, etc.) is attested from late 14c.; that of "track down, follow the trail of" is early 15c., from trace (n.1). Sense of "draw an outline of" is first recorded late 14c. Meaning "copy a drawing on a transparent sheet laid over it" is recorded from 1762. Related: Traced; tracing.