early 13c., from O.Fr. membre (11c.), from L. membrum "limb, member of the body, part," ptobably from PIE *mems-ro (cf. Goth. mimz "flesh"). Specific sense of "penis" is first recorded mid-14c., from L. membrum virile. In English, "member of the body" is the original sense; that 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 mid-15c.