It's a very local (Singaporean) slang widely used within one of my cliques at one point.
I found myself saying "Can Is Can" very often whenever I was streaming a challenging game, and wanted to remind myself that I CAN do it.
When I was affiliated on Twitch back in 2017, I had the option to have my own emotes.
I decided to turn that catch phrase into an emote, and that's when this whole "Can Is Can" culture caught on in the community!
Whenever you think you can't do something, tell yourself #CanIsCan! Can Is Always Can!
We are all about that can-do attitude!