Green’s Dictionary of Slang

1. well.

1737		Pope Mother Gin 25: When rum-rigg’d at Smithfield’s annual Shows, To Drurian Nymphs we pay our solemn vows.
1741		Canting Academy, or the Pedlar’s-French Dict. n.p.: Peck rum, Peck quer Eat much, eat little.

2. smartly.

1833

‘Life In London’ Swell!!! or, Slap-Up Chaunter 11: To come it rum – the time of day, / Is white topper and blue fogle.

3. strangely, eccentrically.

1823

‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 152: ‘Come it rum,’ to talk oddly.