drig drag drug?

[Kathleen E. Miller]

Is there a particular term for switching a regular verb form to irregular?
How bought the other way around ? [Which would make more sense to me.]

So two president's in a row - last one said "swole" this one here comes up
with "drug." Am I correct in guessing its a Southern thing? (Both words
with an early history - the original form maybe?)

Any more common examples?

He's written on this before, with Clinton's swole - but he wants to jump on
Bush's drug with a fresh take and new knowledge.

Thanks,

Kathleen E. Miller
Research Assistant to William Safire
The New York Times