Green’s Dictionary of Slang

pill-box n.

1. joc. use of SE pill-box for anything small, circular and box-like.

(a) a coffin.

[US]T. Haliburton Clockmaker III 82: They end up by being packed up in a snug pill-box in the same grave-yard.

(b) a pulpit.

[UK]C. Kingsley At Last (2007) 207: Getting up to preach in a sort of pill-box on a long stalk .
[UK]Congregationalist May 374: ‘Pill-boxes’, as pulpits are sometimes appropriately called .

(c) a soldier’s hat.

[UK]R.D. Blumenfeld Diary 27 June (1930) 17: This is ‘the swagger mark’ [...] It comes from the pill-box, which protects only a small portion of the head and forehead from the sun.
[UK] (ref. to 1910s) J. Franklyn Cockney 169: Here comes the Boys’ Brigade / All smothered in marmalade / With a tuppenny ’a’p’ney pill box / And half a yard o’ braid.

(d) a small brimless hat.

[US]Minneapolis Jrnl (MN) 6 Feb. 34/1: The ‘pillbox’ headgear is really not so big around as a respectable pancake.
[US]Mani News (Honolulu) 24 Dec. 3/1: Severely plain, but very smart. The Pillbox and the Flowerpot hat.
[US]Sun (NY) 2 May 16/1: A mite of a girl in a pillbox hat.
[US]E. De Roo Young Wolves 37: She wore a pert little pill-box fur hat and an open fur coat.

2. (US) a revolver, a pistol [pill n. (1e)].

[US] ‘South-Western Sl.’ in Overland Monthly (CA) Aug. 126: Among the names of revolvers I remember the following: Meat in the Pot, Blue Lightning, Peacemaker, Mr. Speaker, Black-eyed Susan, Pill-box, My Unconverted Friend.
[US]E.L. Wheeler Deadwood Dick in Beadle’s Half Dime Library I:1 84/1: Harris, (who now held a cocked pill-box in each hand).

3. in medical contexts [pill n. (6)].

(a) a small carriage [such carriages were typically used by doctors].

[UK]T.J. Mathias Satire 33: [note] Sir Charles's bye-name of the Pill-box, conferred on the other carriage, will need no explanation .
[UK]Era 6 June 11/1: He can get along speedier to the rescue on his trotters, than all the balance of his fratenity in their 'pill-boxes'.
[UK]Dickens Little Dorrit (1967) 441: She drove into town in a one-horse carriage, irreverently called at that period of English history, a pill-box.
[UK]Hotten Sl. Dict. 201: PILL-BOX, a doctor’s carriage.
[UK]Sl. Dict.
[Aus]Bulletin (Sydney) 20 Mar. 2/1: The days of steady-going ‘pill boxes’ – medical English for ‘brougham’ – died out with door knockers.
[Aus]C. Crowe Aus. Sl. Dict. 58: Pill Box, a doctors carriage.

(b) a doctor; thus pillbox crew, the medical profession [note pre-WWII London taxi-driver jargon The Pill-box, Harley Street, site of many private consulting rooms].

[US]Salt Lake Herald (UT) 13 Aug. 5/3: The best of all the pill-box crew [...] Are the doctors who have most to do / With the health of a hearty man.
[UK] ‘’Arry in ’Arrygate’ in Punch 24 Sept. 133/1: ’Twas screwmatics and liver, old Pill-box declared.
[US]Perrysburg Jrnl (Wood Co., OH) 6 Oct. 2/6: Van Sharp- How is he getting on, doctor? Dr. Pillbox- I don’t think he will live a month.
[US]Dly Public Ledger (Maysville, KY) 29 July 4/1: The game of baseball [...] between the Doctors and the Druggists of this city, proved amusing [...] the score stood thusly at the end of the sixth inning when the Pillbox crew threw up the sponge.
[Aus]‘Henry Handel Richardson’ Aus. Felix (1971) 168: I’m with you, you old pill-box [...] You’ll cut a jolly sight better figure as an M.D.