"on the same side of the body," 1907, from Latin ipse "self" + lateral (adj.). Related: Ipsilaterally.
c. 1300, "body part or organ, an integral part of an animal body having a distinct function" (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" (source also of Sanskrit mamsam "flesh;" Greek meninx "membrane," mēros "thigh" (the "fleshy part"); Gothic mimz "flesh").
In common use, "one of the limbs or extremities." Especially "the sex organ" (c. 1300, compare Latin membrum virile, but in English originally of women as well as men). Figurative sense of "anything likened to a part of the body" is by 14c., hence "a component part of any aggregate or whole, constituent part of a complex structure, one of a number of associated parts or entities."
The transferred sense of "person belonging to a group" is attested from mid-14c., from notion of "person considered in relation to an aggregate of individuals to which he or she belongs," especially one who has united with or been formally chosen as a corporate part of an association or public body. This meaning was reinforced by, if not directly from, the use of member in Christian theology and discourse from mid-14c. for "a Christian" (a "member" of the Church as the "Body of Christ"). Meaning "one who has been elected to parliament" is from early 15c.
"bone of the spine," early 15c., from Latin vertebra "joint or articulation of the body, joint of the spine" (plural vertebræ), perhaps from vertere "to turn" (from PIE root *wer- (2) "to turn, bend") + instrumental suffix -bra. The notion would be the spine as the "hinge" of the body.
"to cross a body of water by walking on the bottom," 1610s, from ford (n.). Related: Forded; fording.
mid-15c., "box, case," from Old French tronc "alms box in a church," also "trunk of a tree, trunk of the human body, wooden block" (12c.), from Latin truncus "trunk of a tree, trunk of the body," of uncertain origin, probably originally "mutilated, cut off," and perhaps from PIE root *tere- (2) "cross over, pass through, overcome."
The meaning "box, case" is likely to be from the notion of the body as the "case" of the organs. English acquired the "main stem of a tree" and "torso of the body" senses from Old French in late 15c. The sense of "luggage compartment of a motor vehicle" is from 1930. Railroad trunk line is attested from 1843; telephone version is from 1889.