Green’s Dictionary of Slang

a very hard worker.

1910		Lincoln Jrnl Star (NE) 13 June 11: Asked who could have been chosen instead by unperceptive authorities. ‘Swotters’ answered their visitor.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 198: They look down upon one who has to work hard to keep first place. Such a person is a ‘swotter’, ‘swotpot’, or ‘stewpot’.