Green’s Dictionary of Slang

to treat to a drink.

1909

J. Ware Passing Eng. of the Victorian Era 86/2: Comb and Brush (Rhyming). Lush. At one time this word signified ‘drink’, and drink only. ‘Won’t yer lush us?’ meant Will you not pay for some drink for us? Now the word has been extended in its meaning, and includes all shapes of liberality. ‘Jack lushed us all three to the Surrey Theayter.’.