You are right because the word écuyer ( in french ) came from the latin word "scutarius" the one who wear a shield but the english is derivative here of the french because you had a vast définition of the word :
(Remember Henry II and Richard Lionheart graves are in France)
There was écuyer, young who served a knight and and wear his shield
There was an écuyer tranchant, who cut and serve meat at the prince's table
Also a title given to simple "gentilhomme"
Also the title of the steward of a prince's stable
Also the title of somebody who teach equitation in academies, by extension an excellent horse rider
Also écuyer de bouche; the "maître d'hôtel" of a great house
In hunting it's also the name of a young deer who follow an older one
Also name given by a winegrower to a false burgeon
But in équitation came from equus
Ecuyer tranchant came from escarus
It's during feudal period that the word took different meanings in Roman world ( Burgundy, Provence, Spain, Portugal,Italy ) english : squire, esquire
In french litterature
XI cent Ne n'i adeist [que n'y arrive] esquier ne garçon, Ch. de Rol
XII cent Uns escuers vint pognant la ferrée
Also coins name ( derivative Portugal) Escudo