Japanese verb to say


I was wondering about something that occurs in Japanese I've seen quite often
but have yet to find an explanation. I know the Japanese verb to say is 言う,
and I know that sometimes you can simply end a sentence with って to indicate
implicitly that 言う follows. But I've also seen the following:

[sentence]-っつの such as in the following 大丈夫っつの translated to mean: I said I'm
fine.

My question is where does this っつ come from? I'm guessing the の is as in
何をしているの, but the っつ puzzles me. I'm guessing that it's some sort of colloquial
speech style such as saying わかんない vs 分からない, and if that's the case, the only
verb I can think of is 伝える.

Can anyone elaborate?

