frag (v.)youdaoicibaDictYouDict[frag 词源字典]
by 1970, U.S. military slang, back-formed verb from slang noun shortening of fragmentation grenade (1918), which was said to have been the weapon of choice over a firearm because the evidence is destroyed in the act. Related: Fragged; fragging.[frag etymology, frag origin, 英语词源]