hos·tler 
(hŏslər, ŏs-) also os·tler (ŏs-)
(hŏslər, ŏs-) also os·tler (ŏs-)n.
1. One who is employed to tend horses, especially at an inn.
2. One who services a large vehicle or engine, such as a locomotive.
[Middle English, from Anglo-Norman hostiler, from Old French hostel, lodging; see HOSTEL.]