To join hands in agreement or pledge, especially as part of a marriage or contract, or to bind by a handclasp.
From hand + fast (meaning 'firm' or 'secure'), Old English handfæstan meaning to hold by the hand. This was a binding gesture predating written contracts.
A handfast was a legitimate medieval marriage practice where couples joined hands in agreement, and if they parted after a year, the marriage was dissolved—it was essentially a trial marriage, and some historians see it as an early form of relationship flexibility.
Complete word intelligence in one call. Free tier — 50 lookups/day.