Holy cow, I wrote a book!
If you spend time in kernel mode, you're accustomed to seeing functions
with two-letter (or occasionally, three-letter) prefixes
that indicate which component they belong to.
What does the "Zw" mean?
The people who chose the letters wanted to pick something that
was unlikely to collide with anything.
Perhaps they had a prior bad experience with having chosen
a prefix, only to find that somebody ahead of them claimed it already?