Hi Kitty. Thank you for your insightful and interesting question.
BootSlick55 is my username and was chosen for its layered meanings.
Primarily, it alludes to my liking for women wearing boots, especially PVC, hence the Boot and the Slick (i.e. shiny).
Also, those with a boot fetish tend to be interested in being dominated by those boot-wearing women (i.e. boot licking) but I am not one of that type so hence the capital S and not the capital L. A less than alert reader will be fooled, while those on their toes will pick up the subtle difference.
Also also, the capital letters B and S form an acronym BS. This stands for 'horse manure' and points to the fact that I am almost wholly dishonest in the content of my posts. Why? Because this is the internet and should be treated as such.
Also also also, the 55 is a numerical repetition, and therefore easier to remember than two different numbers. It could be any repetitious number. I chose 5 because the two 5's add up to 10, and this is an emoticon that can be interpreted as 'squinty eyes and open mouth', a representation of the human face during coitus. And that, Kitty, at the end of the day, is what we are all here for (here = both the planet and the website).
All very obvious, Kitty, but it doesn't hurt to remind you. Here's a nudie pic: