The choice to call in French was not arbitrary.

French was the language of the voyageur culture that staffed the canoe brigades.

If you saw canoes on the Columbia River in 1814, those canoes were almost certainly operated by voyageurs.

The crew would speak French.

Calling in French was the most direct possible communication: it signaled not just “we need help” but “we are part of your world.”

The boys knew this.

Children who grow up in multilingual environments develop an intuitive sense of which language to use with which interlocutor, often before they can articulate the reasoning.