A touching between two things. Also the person reachable through it, named for the touch rather than the bond.
Latin contactus, past participle of contingere (to touch closely), from com- (together) + tangere (to touch); a touching between two things, extended to the person reachable through that touch.
Latin tangere is to touch, and the word never promises anything past the touch itself, no closeness, no history, only the fact of reach. A person named as a contact is named for being reachable, not for anything shared beyond that.