where does "CARD18" come from?

[wempwer at gmail.com]

Hello,

I was wondering where the names of various data types listed here may
come from:
http://www.x.org/wiki/XSessionManagementProtocol#Data_Types

Most of them are clear, but these ones picked my interest:

 CARD8
 a one-byte unsigned integer

 CARD16
 a two-byte unsigned integer

 CARD32
 a four-byte unsigned integer 

Do you know what is the etymology of these type names? Do they mean
"character...", but what does "d" stand for? In Lisp "car" is a
function that returns the first element of the list but I think Xorg
has nothing to do with Lisp.

History is interesting ;)
-- 
<wempwer at gmail.com>