OED on "stiff"
Posted by R. Berg on February 08, 2002
In Reply to: Stiff drink posted by Marian on February 08, 2002
: : Why "stiff" drink?
: : psi
: I've always thought it was this: put enough alcohol in a drink, and even a veteran drinker may conceivably jerk his/her head back from the glass--almost recoil--after the first taste. Conceivably the drinker's torso appears to stiffen up, although I think that this body language is sometimes affected playfully between friends as a gesture of appreciation for a well-prepared concoction.
The Oxford Engl. Dict. has three broad divisions of meaning for "stiff" as an adjective: I. Rigid; not flexible or pliant. II. Strong. III. Hard, difficult. In section II, most senses are obsolete, including "Of a drinker: 'Hard,'"exemplified by "The Sweitzers are for the most part Souldiers, and stiffe drinkers" . Only two senses are not obsolete: "Strong, violent (of wind)" and "In modern use, of liquors: Strong, potent. Now only of spirits-and-water." 1813: "Mr. Jenkins . . . to the last 'belted' his three bottles of stiff port after dinner." 1883: "Each had a good stiff glass of brandy grog."