defendyoudaoicibaDictYouDict[defend 词源字典]
defend: [13] Defend comes via Old French defendre from Latin dēfendere ‘ward off’, a compound verb formed from the prefix dē- ‘off, away’ and an element that survives elsewhere only in other compound forms (represented in English by offend). It has been suggested that this is related to Sanskrit han- ‘strike’ and Old English gūth ‘battle’, and that it can be traced ultimately to a prehistoric Indo-European *gwendh-.

Defend had not long become established in English when it produced the offspring fend, dispensing with the first syllable. This in turn formed the basis of the derivatives fender [15] and forfend [14]. Fence likewise comes from defence.
=> fence, fend[defend etymology, defend origin, 英语词源]
defend (v.)youdaoicibaDictYouDict
mid-13c., from Old French defendre (12c.) "defend, resist," and directly from Latin defendere "ward off, protect, guard, allege in defense," from de- "from, away" (see de-) + -fendere "to strike, push," from PIE root *gwhen- "to strike, kill" (see bane). In the Mercian hymns, Latin defendet is glossed by Old English gescildeð. Related: Defended; defending.