1785. Grose, Dict. Vulg. Tongue, s.v. A composition used by
distillers to make spirits appear stronger than they really are.
1828. G. Smeaton, Doings in London. Maton, in his ‘Tricks of Bakers
Unmasked,’ says alum, which is called the Doctor, ground and
unground, is sold to the bakers at fourpence per pound.
3. (licensed victuallers’).—Brown sherry. [Because a ‘doctored’ (q.v.),
wine. Cf., sense 2.]