Equerry: a personal attendant of a member of the royal family.

Historically, the equerry was the royal stable. The equerry was also the name of those in charge of the horses of a nobleman.

This word looks like it desperately wants to derive from the Latin word equus, which means horse. It matches up in definition and in spelling. It would be easy to believe that it does, in fact, derive from equus. But, it does not.

No. The word equerry comes from the French écurie (stable). The French word comes from Latin scuria (stable), which itself comes from the Old German word scura (barn). In modern German, barn is Scheune.