What is the origin of the term "kitty" as in a "kitty" box? For
example an company money box that employees contribute to subsidize
office snacks, etc.

Hello.

From The American Heritage Dictionary of the English Language: Fourth
Edition:

"kitty... NOUN...
1. A fund made up of a portion of each pot in a poker game. 2. A pool
of money, especially one to which a number of people have contributed
for a designated purpose. 3. See widow (sense 3).
ETYMOLOGY: Probably from kit1"
Hosted by bartleby.com:
http://www.bartleby.com/61/10/K0081000.html

The origin of "kit" is: 
"Middle English kitte, wooden tub, probably from Middle Dutch."
Hosted by bartleby.com:
http://www.bartleby.com/61/85/K0078500.html

Thus, the word generally refers to the "pot" in card games such as
poker. It apparently comes from the Middle English "kitte" (wooden
tub).

search strategy: 
google groups, kitty, money, poker

I hope this helps.

Having just left a cafe thats promotes itself as the
"Kitty...something, something cafe" with plenty of stuffed pussycats
around the windows I have come in here thinking I was going to find
definitions related to the feline version of the term "kitty".