Origin of the name unknown. Previously official.

A bit of trail on the Fraser [possibly Shale Hill]
Photo: Mary Schäffer, 1908
Whyte Museum of the Canadian Rockies

Before the building of the railroads and the highway, the steep hill east of Mount Robson was the most treacherous section of a difficult trail between Yellowhead Pass and Tête Jaune Cache. When the “Overlander” gold seekers came to the hill in 1862, they unpacked their horses and carried the loads on their own shoulders.

British adventurers Viscount Milton and Walter Butler Cheadle passed in July, 1863:

We came to a place where the trail passed along the face of a lofty cliff of crumbling slate. The path was only a few inches in width, barely affording footing for the horses, and midway a great rock has slipped down from above, resting on the narrow ledge by which we had to pass. This completely barred the way, and the perpendicular cliffs rendered in impossible for us to evade it by taking any other route. We therefore cut down a number of young pine trees, and using them as levers, set to work to dislodge the obstacle. After an hour’s toil, we succeeded in loosening it from its position, and with a single bound it rolled down with sullen plunge into the deep river, far below. We then led the horses past, one by one, with the greatest caution. The path was so narrow and dangerous, that we gave it the name of Mahomet’s Bridge.

James McEvoy surveyed in the Yellowhead. Pass region in 1898:

Issuing from Moose Lake the Faser moves slowly along in a wide stream for two or three miles, then it narrows, and taking a steeper grade, hurries rapidly downward. Two and a half miles below the lake, the old railway location line crosses from the north to the south side of the irver. Some distance further on, the valley becomes more confined, as the mountains on the north side now close in upon the river, similarly to those on the south; and, at a distacne of eight miles in a straight line from the lake, the trail is forced to seek a passsage by a narrow foothold scooped outof the face of crumbling rock overhanging the river.

Mary T. S. Schäffer wrote of her explorations in 1908:

The last day’s travel to Mount Robson was a great improvement on anything we had had since leaving the main Athabasca. The moment we started, the valley began to narrow and close in on the river. At places where we could gaze down upon the water fighting its way through huge rocks, we blessed the steady little feet beneath us picking a way so calmly over the treacherous trail, for a slip or a stumble meant the river two hundred feet below.

Presumably descriptive.

Alfred Richard Cecil Selwyn
Wikipedia

The First Canadian Pacific R.R. and Geological Survey parties for British Columbia, July 22 1871 Left to right : L. N. Rheaumis, Roderick McLennan, A. S. Hall, West West Ireland, Alfred Selwyn, Alex Maclennan, Walter Moberly, C. E. Gilette, James Richardson, — — McDonald, George Watt.
Toronto Public Library

Geological Survey party in camp at Canoe River, October 14, 1871. Alfred Selwyn at centre with John Hammond (left centre) and Benjamin Baltzly (right centre)
Toronto Public Library

“At Moose Lake, the distance to Canoe River is only 18 miles south-westerly in a straight line,” wrote James McEvoy [1862–1935], who surveyed the area in 1898. “The intervening range of mountains, to which the name of Selywn Range is given, delivers most of its waters into the Canoe and McLennan rivers to the south-east, leaving a precipitous descent on the other side from the watershed to the Fraser River.”

In 1871, Alfred Richard Cecil Selwyn (1824-1902), then Director of the Geological Survey of Canada, made a journey from Kamloops to Tête Jaune Cache and ascended the Fraser River some distance above Moose Lake. Selwyn accompanied railway engineer Roderick McLennan on his survey of the Yellowhead Pass, coming along to study the strata of the area. Selwyn made careful notes of the geology in his field book until, somewhere in the Albreda River area, his horse ate the book. In 1875 Selwyn did field work for the Canadian Geological Survey on the Fraser and Peace Rivers.

Selwyn was born at Somerset, England. He was privately educated, and became assistant geologist on the staff of the Geological Survey of Great Britian. From 1852 to 1869 he was director of the Geological Survey of Victoria, Australia. From 1869 until his retirement in 1895 he was director of the Geological Survey of Canada. In 1852 he married Matilda. He was a fellow of the Royal Society, of the Geographical Society, and of the Royal Society of Canada, of which he was president in 1896. He died at Victoria, British Columbia.

Perhaps named for Jasper mountain guide Hans Schwarz, who ascended Mount Robson at least 12 times, or perhaps from the German word for black, according to Banff mountain guide Lloyd “Kiwi” Gallagher.

This feature was named by the Alberta-British Columbia Boundary survey in 1921. “Scarp” is short for escarp, a steep bank or wall.

George Monro Grant [1835–1902], on first seeing the Rocky Mountains in 1871, said, “The line was defined, and the scarp as clear, as if they had been hewn and chiselled for a fortification.”