SHAKE all ingredients and strain into ice-filled glass.
Characterful rum leads with gin and whiskey playing supporting roles with hints of citrus.
Jack is a generic name for all British sailors, derived from Jack Tar in the 18th and 19th centuries. Sailors in those years used high-grade tar in their clothing and hair for waterproofing. The term, "Jack-of-all-trades," described a sailor who could turn his hand to anything, is widely used today.