Mixologist, cocktail historian, and tiki cheerleader martin cate documents the recipe for the twenty seventy swizzle in his fantastic book smugglers cove, where he explains that the name came from the two rums he used: angostura 1919 (a vanilla-tinged column-still aged rum) and the inimitable lemon hart 151, a fantastic overproof demerara rum from guyana. Theres no need to restrict yourself to numerologically-correct rums, though weve made it with a variety of aged and overproof demerara rums, and each one somehow ends up tasting better than the last. That might be the 151 talking, though.