>: I think your correspondent who called beverage left overs "ullage" was simply ignorant.

I don't think we need to be that harsh. the OED goes on:

2. a. (See quots.)
1832 S. Roose Ullaging 5 By knowing the vacuity, and subtracting it from the whole content, leaves the Ullage or the quantity of liquor then in the cask. 1867 Smyth Sailor's Word-bk. 705 Ullage, the remainder in a cask or package which has leaked or been partially used. 1883 Encycl. Brit. XVI. 28/2 The quantity of liquor contained in a cask partially filled and the capacity of the portion which is empty are termed respectively the wet and dry ullage.

b. slang. (See quots.)
1874 Slang Dict. 332 Ullages, the wine of all sorts left in the bottoms of glasses at a public dinner. 1889 Pall Mall G. 21 Aug. 2/1 ‘Pray what is “ullage”?’ ‘The washings out of casks, sir,’ replied my friend.