supine: [15] Supine means literally ‘lying on one’s back’. It comes from Latin supīnus. This was derived from a prehistoric base *sup- ‘up’ which also produced Latin super ‘above, over’ (and summus, source of English sum), so the word’s etymological meaning is presumably ‘with the front of one’s body upwards’. The metaphorical sense ‘inactive’ evolved in Latin. The origins of the use of supine as a noun, to designate a type of ‘verbal noun’, are not known. [supine etymology, supine origin, 英语词源]