Arbitrarily Meaningful
No need to feel guilty about dropping the ball on "Xerox."1 The term is indeed arbitrary and meaningless in the only meaningful way possible; that is, legally with respect to trademarks. Xerox is not a term commonly used, either now (but for Xerox's use of it) or in classical times. While "xerography" may technically mean "dry writing," Xerox is no less fanciful than whatever would be the term for thin film, as derived by combining words that never have been used in that combined form to mean anything.
To 99% of us, "Xerox" would be arbitrary and meaningless had not the company put it to use. The fact that the odd classical scholar found in the odd classics department (fewer and farther between these days--both the scholars and the departments) might understand the meaning does not change things. Indeed, one could read a good deal of Greek...