The earliest reference to this mountain chain is that of John Knight, governor of York Factory who, in his diary for 1716, states that Indians had told him that very far to the west there were prodigious mountains so high "they cannot see the tops without it be clear weather." The first mention of their present name is to be found in Legardeur St. Pierre's journal for 1752, which refers to the 'Montaignes de Roche.' 'Rocky Mountains' is a translation of the Cree name, 'as-sin-wati.' Seen from the east across the prairies, they appear as a great rocky mass."

PLace Names in Canada, from Maeve's link at http://www.spiralroad.com/sr/pn/r/rocky_mountains.html above.