Green’s Dictionary of Slang

bum’s rush n.

also rush
[bum n.3 (1) + SE rush, a sudden onslaught; the origin of the phr. came in the saloons of late 19C New York where vagrants and other hungry people attempted to take advantage of the sometimes sumptuous free lunch counters, which were meant for drinkers only]
[20C+] (orig. US Und.)

1. a rejection; usu. as get... or give... .

2. forcible movement.

3. (also fool’s rush) forcible ejection, esp. from a bar or club; esp. as get or give the (bum’s) rush.

4. a military defeat.