tug (n.)youdaoicibaDictYouDict[tug 词源字典]
mid-14c., in reference to some part of a harness;" c. 1500 as "act of pulling or dragging," from tug (v.). Meaning "small, powerful vessel for towing other vessels" is recorded from 1817. Phrase tug of war (1670s) was originally figurative, "the decisive contest, the real struggle," from the noun in the sense "supreme effort, strenuous contest of forces" (1650s). As an actual athletic event, from 1876.[tug etymology, tug origin, 英语词源]