supinity
/s(j)uːˈpɪnɪti/noun
1= supineness.
2The state or position of lying on one's back or (loosely) of lying down. Compare supineness. rare before late 20th cent.
Origin
Mid 16th century; earliest use found in Nicholas Udall (1504–1556), schoolmaster and playwright. From classical Latin supīnitās state of having one's head or body thrown back, in post-classical Latin also indolence, idleness from supīnus + -tās.