traceyoudaoicibaDictYouDict[trace 词源字典]
trace: English has two distinct words trace, but they come from the same ultimate ancestor. This was tractus (source also of English tract, tractor, treat, etc), the past participle of Latin trahere ‘pull’. This passed into Old French as trait ‘pulling, draught’, hence ‘harness-strap’, from which English gets trait [16]. Its plural trais was borrowed by English as trace ‘harness-strap’ [14]. Tractus also formed the basis of a Vulgar Latin verb *tractiāre ‘drag’, which evolved into Old French tracier ‘make one’s way’, source of the English verb trace [14].

A noun trace was also derived from tracier, and this too was acquired by English as trace [13]. At first it denoted a ‘path’ or ‘track’; the modern sense ‘visible sign’ did not develop until the 17th century.
=> attract, contract, tract, tractor, trait, treat[trace etymology, trace origin, 英语词源]
trace (v.)youdaoicibaDictYouDict
late 14c., "follow (a course); draw a line, make an outline of something," also figurative; "ponder, investigate," from Old French tracier "look for, follow, pursue" (12c., Modern French tracer), from Vulgar Latin *tractiare "delineate, score, trace" (source also of Spanish trazar "to trace, devise, plan out," Italian tracciare "to follow by foot"), a frequentative form from Latin tractus "track, course," literally "a drawing out," from past participle stem of trahere "to pull, draw" (see tract (n.1)).

Meaning "move along, pass over" (a path, etc.) is attested from c. 1400; that of "track down, follow the trail of" is early 15c. Meaning "copy a drawing on a transparent sheet laid over it" is recorded from 1762. Related: Traced; tracing.
trace (n.1)youdaoicibaDictYouDict
"track made by passage of a person or thing," c. 1300, from Old French trace "mark, imprint, tracks" (12c.), back-formation from tracier (see trace (v.)). Scientific sense of "indication of minute presence in some chemical compound" is from 1827. Traces "vestiges" is from c. 1400.
trace (n.2)youdaoicibaDictYouDict
"straps or chains by which an animal pulls a vehicle," c. 1300, from earlier collective plural trays, from Old French traiz, plural of trait "strap for harnessing, act of drawing," from Latin tractus "a drawing, track," from stem of trahere "to pull, draw" (see tract (n.1)). Related: Traces.