I’m on [verb]

The English language has no future tense. To refer to the future, we use various strategies with verbs in present tense (some of them auxiliaries):

I will run
I will be running
I shall run
I’m going to run
I am to run next
I’m running tomorrow
I run next Friday

Because we can conceptualise the future and it plays a big role in our lives, we talk about it often. Naturally, then, the ways we talk about it are subject to pressures of economy, resulting in contraction, e.g.:

I will run → I’ll run
I am going to run → I’m gonna/gon’ run
I’m gonna run → I’mna run → I’ma/Imma run

I’ll is acceptable in Standard English; gonna/gon’ and I’mna/I’ma/Imma are not, though you may see them in dialogue or informal writing or use some of them yourself in everyday speech – gonna is especially widespread.

Recently I came across another form: I’m on [verb]. It seems similar to I’ma and I’m gon’, but I don’t know exactly how or when it developed. Here’s the example I saw, in Elmore Leonard’s novel Mr. Paradise:

I’ma share some Walter Mosley and William Labov

The contraction I’ma (also Imma, etc., = I’m gonna) hit the spotlight in 2009 when Kanye West used it while interrupting Taylor Swift at the MTV Video Music Awards (“I’ma let you finish, but Beyoncé had one of the best videos of all time”). Parodies spread and a meme went viral.

But the phrase has been around for decades. Neal Whitman has written helpfully about its development and usage at Literal-Minded (twice) and the Visual Thesaurus; all three posts are worth reading, and there’s more at Language Log if you’re interested.

I’ma in print lags behind its occurrence in speech, but I came across it recently in Walter Mosley’s novel White Butterfly (1992). The third outing of reluctant detective Easy Rawlins, White Butterfly includes several instances of I’ma used in AAVE speech. A few examples: