I don't know if you are missing something, but you are jumping to conclusions. All of these terms were invented in the early 1980's well before object-oriented nomenclature came into wide use.
Originally Posted by db2farmer
A bufferpool is memory allocated for buffering table and index pages. This is known in today's terms as memory cache.
It is a "pool" of individual bits and bytes of memory that are associated together into a single bufferpool. One can have multiple bufferpools in a database.
You might want to read this manual first, and then post here if you have any specific questions. I don't know what you are reading now, but it doesn't appear to do a good job of explaining things:
Here are all the manuals:
IBM - DB2 Version 9.5 for Linux, UNIX and Windows English manuals
M. A. Feldman
IBM Certified DBA on DB2 for Linux, UNIX, and Windows
IBM Certified DBA on DB2 for z/OS and OS/390