The birth of Xtina happened in 2002, as Ms. Aguilera was looking to blast the virginal image that her record label was trying to push.
If the song didn't accomplish that, the video sure as hell did. A dirrty, gritty affair, featuring mud wrestling, furries, and a relatively scantily clad Xtina ended up being an immediate hit and propelled the song to #5 on the pop charts.
The songwriting team included Redman, whose 2001 song "Let's Get Dirty" was a strong inspiration for this single, which Aguilera fought to be the first single from her Stripped album (over eventual megahit "Beautiful").
To go a little bit into how the sausage is made, I like to add a live performance in a lot of these posts. In the case of this song, there are a lot of performances from 2002 and 2003 in which it is not clear whether or not Christina is singing or just lip-syncing (I believe she is singing but using a helper track). Sure, there are a lot of assless chaps, but I like to give you, the reader, a different perspective of the song.
Then I found this full-band performance. No doubt she's singing the hell out of this song here.