Pseudotsuga menziesii named for Archibald Menzies, a Scottish physician and rival naturalist David Douglas.
The MacKendrick got it right, mostly - scientific names are always written in
italics and Douglas-fir is always written with a hyphen, to indicate its false fir status.
The tree's common name honors David Douglas, but the scientific name, as the MacKendrick noted, honors Archibald Menzies, who discovered it on Vancouver Island.
This is a case where good information lets us see our past bad information. When I was in Idaho, I was TOLD that doug fir, was "red fir". So all these years have I been mis-informed? Wonder which we were cutting?
It's fine to call it red fir in Idaho, as most everyone does. However, if you go to California, Red Fir is a true fir (
Abies magnifica).
The problem with common names for plants is any two people can be talking about two totally different species using the same name (Pin Oak is a widely and incorrectly used name for a lot of oaks), which is why it helps to learn the scientific names.