"Polymorphic" is a fancy way of referring the the multi-valence of words, including some acronyms and abbreviations. XP in Windows XP is maybe not the same XP as in eXtreme Programming. Or is it? Maybe we'll never know for sure.
In any case, eXtreme Programming (XP) refers to an evolving discipline (new discoveries every day) aimed at increasing programmer productivity. The Hollywood stereotype of free caffeine-stoked beverages in a cooler, offices conducive to overtime, aren't necessarily up to date regarding the latest practices around pair programming or multitasking.
My XRL is a cross between XP and URL, with a hint of eXtreme roller coasters, like Matt and I patronized that time at Six Flags, about 40 miles north of LA on I-5 (drove by it again just the other day, quite a sight even from the freeway).
XRL might also get decoded as "eXtremely Remote Location" instead of "L for Livingry" (in the sense of "gear," and set opposite "killingry" in Bucky Fuller's lexicon).