(this would me grammatically correct to say this)
He ain't going to the store right now.
(this isn't a correct word because usually a compound word takes out one letter on the word, ain't, if you tried to add a letter to ain't you more than likely wouldn't get anything. But ain't just seems to sound better in syntax.)
A single word that is equivalent to other words such as:
1) Am not
2) Are not
3) Is not
==> Most likely originated in the Southern States of America as it flows easily with their accent but has now been used in many places around the world.
"We aint going."
"He aint going."
He ain't goin' to eat those nasty baked beans.