'Britophile' is a modern formation combining 'Brit-' (from 'Britain') and the Greek-derived suffix '-phile' (from Greek 'philos'), where 'philos' meant 'loving' or 'fond of'.

'Brit-' ultimately goes back to Latin 'Britannia' (used by the Romans for the island) and earlier Celtic names for the island; '-phile' comes from Greek 'philos' and entered English via New Latin and modern coinages (e.g. 'Anglophile'), with these elements combined in modern English to form 'Britophile'.

The formation has always meant 'a lover or admirer of Britain/British things' and has retained that sense in modern usage.