It seems we can track it back to the early 1990s at Apple. Coined by none other than the influential author of The Design of Everyday Things and Emotional Design, Donald Norman.
According to his account:
"I invented the term because I thought Human Interface and usability were too narrow: I wanted to cover all aspects of the person's experience with a system, including industrial design, graphics, the interface, the physical interaction, and the manual." (Buley pg13)
: The User Experience Team of One - Leah Buley