What is 'twas Ain't?
A phrase that combines the contractions 'twas (it was) and ain't (is not), closely meaning "It was not" or "It is not".
In a casual conversation appropriate use would be in the context of disagreement or disapproval.
On January 6, 2008, on a surprisingly warm Sunday evening (A stark contrast from the frigid cold one had to endure the previous days) under the influence of a particular, earthy substance, two Chicago residents named Jason and Carla spoke of fancied and eloquent discourse in the comfort of Carla's bedroom.
As their conversation ran it's natural course, Carla verbally penetrated Jason's psyche, and in doing so planted the seed to would blossom into divine inspiration. Then from the mind to the voice came the words "'Twas ain't!, birthed from Jason's mouth.
Carla: This particular term sounds concurrently Shakespearean and
Jason: 'Twas AIN'T! More specifically, surely our lovechild that is this newfound phrase contains within itself allusions of both Shakespeare and contemporary, Black-urban vernacular.