But oddly enough, despite all the logic-twisting some folks go through to justify their usage, logic is not even a requirement for idioms. An idiom is what it is. Using it requires no logical justification. Those who are familiar with the idiomatic usage of a word or phrase understand it; those who are ignorant of it often simply mis-hear it, and subsequently butcher and mis-use it. Say “pipe them gams!” to a youngster who hasn’t heard it, and it might be picked up in transmogrified form as “like them hams!”, and the wide-eyed, unaware youth will, in due time (or “in do time” as he might say), after repetition of his own butchered usage while remaining unaware of the original phrase, be able to explain the “logic” behind the expression, totally unaware of his error.

So yes, Robert, there are indeed now two idioms: the original clever turn of phrase, and the mistake borne upon the wings of ignorance. Some people might think there’s no difference between a clever turn of phrase and an ignorant mistake, but they have another think coming. Those mistakes are telling, and elicit smiles.

There was once one idiom, now there are two, and they are both perfectly logical. There is simply no logical basis for saying “another thing coming” is wrong. It’s like “card sharp” vs. “card shark”. There is nothing wrong with either. Sharp may have been original, but card shark has connotations of someone who is not just skilled with cards, but someone who will take advantage of you, like a pool shark.