It's from the Simpsons and that is pretty much exactly the context that it first appeared in! Here's an excerpt from the "Made-up words" article on the simpsons.wikia.com:
When schoolteacher Edna Krabappel hears the Springfield town motto "A noble spirit embiggens the smallest man," she comments she'd never heard of the word embiggens before moving to Springfield. Miss Hoover replies, "I don't know why; it's a perfectly cromulent word".
I wonder if you can use "cromulent" to guess the age of a person. Older people would not have watched the Simpsons in the early 90s. Younger people very likely missed this obscure episode. I would guess an age of the user to be 30-35.
The episode was first aired in Feb ‘96, at which point I was 20, and in college. At this point the show was still quite popular with my friend group. I am currently 42. You might need to increase your upper bound on the age range.
You're not far out, but I must have missed that episode originally and only watched it in the last few years. I possibly also learnt it from Reddit first.
Others have filled in the detail of origin and meaning. Yes, my intent was to use another neologism to add an ironic tone. Language is always changing.
