Green’s Dictionary of Slang

boot, the n.

1. [late 19C+] ejection, dismissal, defeat in all cases, esp. when sudden and ruthless; thus get the boot, to be thrown out, both of a place or one’s employment; give someone the boot

2. [late 19C+] an act of kicking; in phr. give someone the boot

In phrases

give someone the boot (v.) [late 19C+]

1. to dismiss from a job, to throw out; to end a relationship with.

2. (also ...the heel, ...the boots) to give someone a kicking; also fig. use.

order of the boot (n.) (also royal order of the boot)

[late 19C+] dismissal, rejection; usu. as get/give the order of the boot.

put the boot in (v.) (also get in the boot, get the boot in, lay in the boot, put in the boot, put the boot(s) to, put the boots into, sock the boot in, stick the boot in) [20C+] (orig. US)

1. to kick someone during a fight; thus in with the boot, no holds barred.

2. (also sock a boot into) in fig. use.

put the boots to (v.) (also throw the boots into)(US)

1. [late 19C+] to give a kicking to; thus get the boots, to receive a kicking; also fig. use.

2. [late 19C+] to victimize, to treat harshly.

3. [1920s+] (also get the boots, put the boots on) to have sexual intercourse with; to rape.