Green’s Dictionary of Slang

mixum n.

[the mixing of medicines]

1. an apothecary.

[UK]H. Glapthorne Hollander I i: Sir, I am sent from Mr. Mixum, your Apothecary.

2. a vintner.

[UK]Bilker Bilk’d 3: Mixum, that Rogue of a Vintner.