Originally: †a unit of length based on the breadth of a hand, although varying in size according to period and locality; four digits, equal to three inches (approx. 7.8 cm); also figurative ; compare "hand", "palm"; (obsolete). In later use: a distance or length likened to the width of the hand.
Mid 16th century; earliest use found in The New Testament. In some forms from hand + breadth.