Named by Walter Alfred Don Munday [1890–1950] during his explorations in the Cariboo Range:

The dominant feature of the scene was the magnificent mountain which the Carpé-Chamberlin party proposed to name Mt. David Thompson (11,250 ft.) in the belief that the pass north of it was the true source of the North Thompson River. Northward of this pass gleamed an ice guarded mountain which we refer to as Mt. Hostility (11,000 ft.). The sunlight threw into relief the whole expanse of glacier, the lower part marked by great concentric ridges where the dry glacier describes an arc of nearly 90 degrees.

Munday doesn’t elucitate on the reasons for the name “Hostility,” but the party experienced unpleasant weather.

This unofficial name was superseded in the Premier Range commemorations.