Often used in text messages as form of slang. A mixture of "legit" and "literally", can be used in certain situations on a daily basis when put into context, the term is usually used to emphasise and convince the listener/reader.
"She legitallypunched him in the face!" "I've legitallyhad enough of her"
When an event or individual is so legit, that the single term "legit" is too commonplace to describe it. Multiple legitly's can be included for added effect.
Man #1: Dude, my wife just gave birth to a son!
Man #2: Nice! What did you guys name him?
Man #1: Perry.
Man #2: THAT'S LEGITLY LEGIT