A more thorough explanation:

Definition: Hostler ([h]os-lər). [from hosteler] Archaic.

1. A stableman; an ostler.
2. An innkeeper.

By the 16th century, this term had lost its “innkeeper” sense, and referred exclusively to a stableman.

Example 1: The hostler took care of the horses at the stable.

Example 2: The hostler at the inn made sure the guests' horses were well-fed and rested.

These examples illustrate the two meanings of the term hostler. In the first example, the hostler is a stableman who takes care of the horses. In the second example, the hostler is an innkeeper who takes care of the guests' horses. However, by the 16th century, the term hostler lost its meaning as an innkeeper and only referred to a stableman.