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
