Conceivably derived from "exactamente," Spanish for "exactly."
It is used primarily by U.S. non-Spanish speakers. The Fonz, a hip irreverent character on the 50s TV show The Happy Days is responsible for some of the earliest recorded utterances though it's likely to have been in use before then.
It is also a favorite expression of Cam's. :)
Will we be Ebidta positive in 3rd quarter of 2020?