Green’s Dictionary of Slang

pop off v.1

[SE pop, to move]

1. [mid-18C+] to die.

2. [19C+] to depart.

3. [1990s+] to happen, to start.

In phrases

pop off at the handle (v.)

[mid-19C] (US) to reject, to dismiss.

pop off the hooks (v.)

[19C+] to die.