Green’s Dictionary of Slang

keep buggering on, i.e. persevere, stick to the job.

2002

(con. 1940s) Eliot A. Cohen ‘Supreme Command’ National Rev. Online 18 Jun. 🌐 Churchill, far from being an aristocratic lounger, was a glutton for work; his motto to his secretaries during the Second World War was ‘KBO’ — ‘Keep Buggering On.’.