Around the time of Invasion, they introduced the idea of those born with the Meta-Gene, i.e. the latent potential for super powers. How the Meta-Gene was awakened could vary, those powers didn't always manifest naturally, sometimes it was triggered by some weird accident, or forcibly manifested by alien manipulation, or... but if you had super-powers, you were born with the Meta-Gene.


-M

I have seen the term mutant used in DC comics though not as prominently as Marvel does.

Batman #165 featured the story of "The Man Who Quit the Human Race!"  As the second issue of Batman during his New Look phase it might be a significant indicator of what DC felt could pass as serious subject matter at a time when they were planning to get away from silly storytelling (ie. anything involving aliens, Bat-Mite, time travel, etc.).

Not that Batman suddenly started fighting mutants on a regular basis (in fact, this is the only example I can think of off the top of my head from this period) but it seems like something was going on in 1964 that the subject of mutants carried a sort of 'well, you could almost pretend that this is believable subject matter' gravitas in the same way that if you tossed in the word 'tachyons' into Barry Allen's vocabulary as he discussed Gorilla City, things seemed more adult over at The Flash.



Though the Superman of 2965 wasn't as unique as DC tried to pretend (his co-workers, boss, secret identity, job, and so on were all just updated versions of what he was doing in 1965) they did, at least, make the effort of coming up with an original worst enemy for him instead of just introducing Klex Kluthor 2965).




Muto wasn't born with his powers (he actually got them when a future Superman screwed up and accidentally sent him and his parents to an alternate dimension where robots experimented on him) but once again, we have the word mutant (or at least a variation of it) making its way into the DC lexicon.