memberyoudaoicibaDictYouDict[member 词源字典]
member: [13] Latin membrum originally meant ‘part of the body, limb, organ’ (it has been connected tentatively with various words in other Indo-European languages meaning ‘flesh, meat’, including Sanskrit māmsám and Gothic mimz). But it was early broadened out metaphorically to ‘part of anything, one that belongs’, and brought that meaning with it via Old French membre into English.

The original sense still survives, though, particularly with reference to the ‘penis’ (an application that originated in Latin – membrōsus denoted ‘having a large penis’). Derived from Latin membrum was the adjective membrānus. Its feminine form membrāna was used as a noun meaning ‘skin covering an organ or limb’ – whence English membrane [16].
=> membrane[member etymology, member origin, 英语词源]
member (n.)youdaoicibaDictYouDict
late 13c., "sex organ" (compare Latin membrum virile, but in English originally of women as well as men), also, "body part or organ" (in plural, "the body"), from Old French membre "part, portion; topic, subject; limb, member of the body; member" (of a group, etc.)," 11c., from Latin membrum "limb, member of the body, part," probably from PIE *mems-ro, from root *mems- "flesh, meat" (cognates: Sanskrit mamsam "flesh;" Greek meninx "membrane," meros "thigh" (the "fleshy part"); Gothic mimz "flesh"). In English, sense of "person belonging to a group" is first attested early 14c., from notion of "constituent part of a complex structure." Meaning "one who has been elected to parliament" is from early 15c.