means The full extent or reach between two points, whether a physical distance, a stretch of time, or the breadth covered by something.

from From Old English 'spann,' meaning the distance between the tip of the thumb and the little finger when the hand is stretched wide — an old, body-based unit of measure that turned the human hand into a ruler. It's kin to Germanic relatives like Dutch 'span' and German 'Spanne,' and likely tied to the root for stretching or drawing tight (the same sense that lets us 'span' a river with a bridge). Hand first, then everything else.