In this message, "XEN" represents the name of an article. The "EN" part of this name is the language code (which was English for the original version). If you're translating to French [fr], you may use XFR, for Italian [it] "XIT", etc. Or you may just keep the "XEN". Just be consistent with what you do with other occurrences of "XEN" (and similar "YEN", "ZEN", etc.). Same thing for "XSW", except the "SW" is the language code for Swahili.