[tallpapab]

Ironic that you refer to an RFC. CC was used in correspondence long before internets and RFCs (as was BCC). It meant "carbon copy" just as you said originally. This is a bit like updating an icon. The icon (actually acronym) was left unchanged and someone thought to call it "courtesy copy" because they must have thought carbon copies obsolete and confusing. Actually, I don't know the genesis of the term "courtesy copy", but I'm pretty sure it was an update.

Sorry this whole rambling note is further evidence that old people (and their icons) don't make sense anymore.