Answer:
XP stands for "Experienced". Microsoft had gained enough experience from their 9x or dos based operating systems like windows 95, windows 98 etc, and from their NT-based operating systems like windows NT 4, 2000. Therefore, they used all that experience to build an operating sytem having features from both the lines, and named it Windows XP, or an experienced windows operating system. I told you what I knew, I could be wrong as well.