Gen.Mannerheim
Grand Moff
Well, this one might just tell us that the English are weirdos. Far as I can tell- by which I mean "as far as I can google", naturally- most Romance and Germanic languages use words literally meaning "horseman" or "rider", like the French chevalier and German ritter, and non-Germanic, non-Romance languages use either equivalent terms, like the Basque zaldun or Welsh marchog, or direct borrowings, like the Irish ridire, Czech rytíř or Albanian kalorës. The only non-English departure from this is the Slovene and Serbo-Croatian vitez, derived from the old Germanic wiking, warrior. The English seem to be the only people in Europe who've derived their word for an armed, mounted warrior and associated lower-gentry with their historical role as retainers, and it's not really self-evident what unique thought-patterns the English might possess that would have lead them to this.
Sometimes, language is just weird for no particular reason, or at least no reason that's particularly satisfying.
I feel that there's probably a correlation between the lack of heavy/light cavalry in late Saxon armies and the evolution the the word knight. The main body of the late Saxon armies was the infantry, particularly the huscarls. By the time of Harold Godwinson, huscarl seems to have meant the personal freemen warriors directly funded by the King,a system started by Knut the Great. However, the English word for Medieval heavy cavalry isn't housecarl.
In the Saxon language, cniht seems to have been a general term for a servant or retainer of a lord. It doesn't take a big mental leap to see how the term for servant would be used to describe this new form of martial retainer imposed by their new overlords.
@Traitorfish Where does the convention of translating the Roman 'equestrian' as 'knight' (which has always bothered me) fit into that?
Do you have a better English term to describe a landed class that was (at least according to the classical sources) responsible for providing mounted military service to the state?