Wolverine’s gift of (sometimes ridiculously overpowered)fast healing has been described as a “healing factor” for as long as I can remember. When did this start?
Probably in the 1970’s, with early Wolverine stories. I don’t remember another term before it.
I have no idea when the term “healing factor” was first used (probably not until the early 90’s, I suspect, maybe in the “Weapon X” serial), but the first mention of Wolverine’s tendency to “heal real fast” is in X-Men # 116 (Dec. '78), and the first time this is verified as a mutant ability (as opposed to just him being really tough) is in the “Days of Future Past” storyline, i.e. X-Men #'s 141-142 (Jan-Feb. '81). Of course, his healing power was much different then, and much less powerful. In “Days of Future Past,” for instance, Future Wolvie is killed when a Sentinel incinerates him - an attack which would barely slow him down these days.
Paul ‘Manhunter’ Kirk was described as having a “healing factor” before Wolverine.
I’ve always wondered: Why “factor”? The word doesn’t make any sense there. It’s a healing “power”. A factor (outside of it’s mathmatical usage) is a piece of information used in a decision-making process: “His buck-teeth weren’t a factor in why Jane turned him down for the prom.”
Also, the first clue about Wolverine’s healing was around X-Men #98 give or take an issue. Up until then, in his 5 or so previous experiences, everyone thought his claws came out of his gloves. Then we saw them pop out of the back of his hands…and there was no blood, no scarring.
In biology, we use “factor” to describe substances or agents that control the way a living system behaves. There are broad categories like growth factors, transcription factors, and clotting factors. Several factors are explicitly named as such: “fibroblast growth factor” (the substance that, when squirted on certain types of connective cells, makes them grow) and “von Willebrand factor” (the clotting factor whose mutation is responsible for a type of hemophilia originally discovered by Dr. von Willebrand). This usage dates back many decades at least.
A little more generally, we use “factor” as a placeholder descriptor for some unknown substance or agent that we believe is responsible for an observable phenomenon. E.g. in early cancer research, someone might have placed a group of cancer cells next to a group of normal cells, and then observed that the normal cells would begin to grow abnormally. Before modern genetics, the early discovery would be limited to learning that this abnormal growth is caused by a “factor” that is secreted from the cancer cells, and that it is a protein that can be isolated by various methods.
Informally, we talk about how a cell or system “decides” how to do something, and in the context of growth factors, how one cell “tells” another cell what to do. That’s similar to the decision-making usage of “factor” that you describe.
“Healing factor” fits right in with all of that.
Personally, I interpret it in the mathematical sense: In the most described and consistent forms, Wolverine can heal from the same things a normal human can heal from; he just does it much faster. So if, say, he heals 100 times faster than normal, that’d be a healing factor of 100. Just using the term without a number attached is thus strictly speaking meaningless (I have a healing factor of 1, after all), but it’s the sort of natural linguistic evolution you’d expect from people talking about such a phenomenon.
I didn’t know any of that—thanks for the extremely cool and informative post! 
I understood it to be like what **lazybratsche **said. I can see why some people less familiar with the bio usage would think what Chronos thought, but no, it’s a “factor” in a biological sense of “weird thing that affects his cells.”