I'll guess...

Structures may refer to the physical structure found in 'core memory' - a carry over from antiquity.
http://en.wikipedia.org/wiki/Core_memory

Areas ? who knows.... Maybe because a chip is masked off and an 'area' has a specific function like cache, cpu, memory, etc. http://en.wikipedia.org/wiki/Computer_storage
http://www.kingston.com/tools/umg/default.asp