Green’s Dictionary of Slang

a fit of yawning, a feeling of laziness, lassitude.

1795		Sporting Mag. Aug. VI 279/1: A certain money lender [...] has nearly run his course – town house and country house gone – and the greys into the bargain! Without some lucky hit, his sun is set.
1890–1904		Farmer & Henley Sl. and Its Analogues.