equison
Groom, ostler, equerry, jockey.
archaic
Once indeed, I confess it, I was very near falling as low: words passed between me and the more favored man of letters, who announces to the world the Works and Days of Newmarket, — the competitors at its games, their horses, their equisons and colours, and the attendant votaries of that goddess who readily leaves Paphos or Amathus for this annual celebration.
Where it comes from
From Latin equīsō (“stable-boy, equison”), from equus (“horse”).
Adapted from the Wiktionary entry equison (CC BY-SA 4.0).