Another where it would be nice to track down a full name. Based on some of his contributions to journals it seems like he was professor and had some knowledge of gaelic and Scottish place names.
A professor at Edinburgh university at some point by the looks of it https://climbing-history.org/library/11427/the-cairngorm-club-journal-no-72
My bet is on William John Watson, although establishing a clear climbing connection seems to be tricky.
Great sleuthing. It would be an amazing coincidence if there was another W J Watson with such an overlapping biography so I'll update the name and add a link to the wikipedia page.