Green’s Dictionary of Slang

1. (also muddle on) to continue drinking although already drunk.

c.1698

B.E. Dict. Canting Crew n.p.: To Muddle on, tho’ so [muddled], yet to Drink on.

2. to have sexual intercourse.

1890–1904

Farmer & Henley Sl. and Its Analogues.

3. to render oneself drunk.

1876

M.E. Braddon Dead Men’s Shoes III 248: He has never been properly sober, muddling himself with gin and beer – dog’s nose, he calls it.