Definition of "gemmen"

Gemmen (says he), you all well know / The joy there is whene'er we meet; / It's what I call the primest go, / And rightly named, 'tis—'quite a treat,' […]

1820, Thomas Moore, W. Simpkin, R. Marshall, Jack Randall's Diary of Proceedings at the House of Call for Genius

Gemmen, have you ordered the peck and booze for the evening?

1821, W. T. Moncrieff, Tom and Jerry