Old fogey, sometimes spelt 'fogy', meaning an excessively old-fashioned, staid person dates from 1780, according to the OED. 'Fogy' did appear a few years later in Francis Grose's Classical Dictionary of the Vulgar Tongue, published in 1785. Grose's entry for 'fogey' is as follows. 'A nickname for an invalid soldier: derived from the French word fougeux, fierce or fiery.' This French origin is still cited by some sources, but is discounted by most etymologists today. A little further on, Grose has an entry for the slang word 'fogram' meaning 'a fusty old fellow'. From this meaning, it is plausible there could be a connection between the two, but because Grose lists 'fogram' as a separate word entirely, the origin of 'fogey' remains obscure. The OED maintains there might be an association with 'fogram' but, on the evidence available, returns a verdict of origin unknown for fogey.