This is a guess off the top of my head, since I don't know for sure. It probably has its origins in old film camera dials, specifically the "landscape" mode in fully automated/computerized cameras of the early 1990s.
I have an old Canon EOS 500 35mm SLR (from 1993) with a Landscape icon on the Mode dial. It doesn't look exactly identical, it has a cloud instead of the sun, but still the two distinct mountain peaks.
Here you can see it between the portrait (head), and macro mode (flower) symbols.
I don't know whether Canon, Nikon or even Fujifilm were the first to use this but I'd happily put a bet on it being a Japanese camera manufacturer.
If somebody has an earlier example, this could easily disprove my theory. I also tried searching early Apple MacOS classic icons, since Apple practically invented the graphical user interface, but couldn't find anything that looks like this at all.
For historical context it's also interesting to note that the first ever version of Photoshop was not released until 1990, and the world wide web did not go public until 1991, and the world’s first commercially produced digital camera you could actually buy was the FUJIX DS-X. Apparently the RRP was $20,000 at the time!!