Green’s Dictionary of Slang

fap adj.

drunk.

c.1597		Shakespeare Merry Wives of Windsor I i: I say, the gentleman had drunk himself out of his five senses. [...] And being fap, sir, was, as they say, cashier’d.
1818		J. Brown Psyche 44: Getting daily fap with ale, / How can he hope — to wear a tail?
1822		R. Nares Gloss. (1888) I 296: fap seems by the context to mean drunk, but has not yet been fully traced. It was probably a cant term.