Regarding its first use - after some digging in my books, I found this interesting article:
"The words wabi and sabi have been closely linked to the aesthetics of the chanoyu tea ceremony since the time of Murata Shuko (1421?-1502). He described his preferences for using as tea wares inexpensive, locally made utilitarian vessels (instead of more finely wrought Chinese objects) as wabi-suki, an expression that, by the 17th century, had evolved into the phrase wabi-cha (poverty tea)...." Rest in below screenshot.
From the excellent book 'Japanese Design - Patricia Graham' (I think it's Ford who put me on that title, so thx for that!)