Green’s Dictionary of Slang

(school) a hard worker.

1888

Times 1 Feb. 12, col. 2: Remember the many epithets applied to those who, not content with doing their work, commit the heinous offence of being absorbed in it. Every school, every college has had its choice nickname for this unfortunate class... such as a ‘sap’, a ‘smug’, a ‘swot’, a ‘bloke’, a ‘mugster’ [F&H].