attachyoudaoicibaDictYouDict[attach 词源字典]
attach: [14] When English first acquired it, attach meant ‘seize’ or ‘arrest’. It is Germanic in origin, but reached us via Old French atachier. This was an alteration of earlier Old French estachier ‘fasten (with a stake)’, which was based on a hypothetical Germanic *stakōn. The metaphorical meaning ‘arrest’ appears to have arisen in Anglo-Norman, the route by which the word reached English from Old French; the original, literal sense ‘fasten, join’ did not arrive in English until as late as the 18th century, as a reborrowing from modern French attacher.

A similar borrowing of Germanic *stakōn into Italian produced the ancestor of English attack.
=> attack, stake[attach etymology, attach origin, 英语词源]
attach (v.)youdaoicibaDictYouDict
mid-14c. (mid-13c. in Anglo-Latin), "to take or seize (property or goods) by law," a legal term, from Old French atachier (11c.), earlier estachier "to attach, fix; stake up, support" (Modern French attacher, also compare Italian attaccare), perhaps from a- "to" + Frankish *stakon "a post, stake" or a similar Germanic word (see stake (n.)). Meaning "to fasten, affix, connect" is from c. 1400. Related: Attached; attaching.