here's the earliest citation plus the one that lends credence to lobscourse:

1706 [E. WARD] Wooden World Diss. (1708) 83 He has sent the Fellow.. to the Devil,
that first invented Lobscouse. 1751 SMOLLETT Per. Pic. (1779) I. ix. 76 A mess of that
savoury composition known by the name of lob's course.