I could be wrong, but I believe the acronyms are: ARC = Automatic Reference Counting (NOTE: not Atomic) ORC = Optimized Reference Counting

The loopy/circular character of the letter 'O' may be a secondary mnemonic since it collects cycles.

I meant "character" as in "nature" not as in the prog.lang "character type"..I just realized that in context this might be confusing. Lol.