Green’s Dictionary of Slang

drop off v.1

[fig. use of SE]

1. to die.

[UK]Foote Maid of Bath in Works (1799) II 208: A few feeble fellows that dropt off with the leaves in October.
[US]H.H. Brackenridge Modern Chivalry (1937) Pt II Vol. I Bk II 442: There are chimney sweepers, who think they will all go to pot, when they drop off.
[UK]Carlisle Jrnl 2 Nov. 4/2: If the old woman should drop off, I should not be very much surprised to see these two farms thrown into one.
[UK]New Sprees of London 21: This crib is kept by a notorious face maker, named Bob Dorkings, the only surviving branch of a family that have all dropped off suddenly, at hot roll time.
[UK](con. 1840s–50s) H. Mayhew London Labour and London Poor II 468/2: All my friends is dropping off. I’m fifty-five, and they was men when I was a boy.
[UK]Sporting Times 15 Mar. 1/5: My physician says I am liable to drop off at any moment with heart disease. He gives me only a couple of months to live.
[US]E. Pound letter 26 Dec. in Paige (1971) 192: On further considerations, better not send copy Cantos to Hardy. He may drop off at any moment.
[UK]H. Ashton Doctor Serocold (1936) 149: You must be pretty busy to-day, with your partner dropping off suddenly like that.
[US]L. Pound ‘American Euphemisms for Dying’ in AS XI:3 199: Dropped off.

2. to retire.

[US]H.L. Williams Ticket-of-Leave Man 20: He dropped off a month ago and was on the pension list ever since.

3. to kill.

[US]‘Armitage Traill’ Scarface Ch. iii: Spingola had been about the first of the city’s gang leaders to enforce his power with a gun and his being dropped off so suddenly was most disconcerting to the other leaders.

SE in slang uses

In phrases

drop off the hook(s) (v.)

to die.

[UK]Era 20 Dec. 5/4: It’s five weeks [...] since auld biddy Hoolijan tuck herself off the hooks .
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[US]L. Pound ‘American Euphemisms for Dying’ in AS XI:3 199: Dropped off the hooks.