Английский Этимологический словарь - span (1)

- "distance between two objects," O.E. span "distance between the thumb and little finger of an extended hand," probably related to spannen "to join, fasten" (see span (2)). As a measure of length, roughly nine inches. Meaning "length of time" first attested 1599; that of "space between abutments of an arch, etc." is from 1725; the verb meaning "to encircle with the hand(s)" is from 1781; in the sense of "to form an arch over (something)" it is first recorded 1633. Spanner (1639), the British name for the monkey wrench, is from Ger., originally a tool for winding the spring of a wheel-lock firearm.