you may have heard of an IC chip named after someone, but have you ever heard of a chip *pin* named after a dog? it's true! the famous 6502 CPU has a pin, S.O., named after 6502 co-designer Rod Orgill's dog, Sam Orgill! (thread) 
of course, the S.O. pin has an official meaning, according to my 1976 MOS Technology hardware manual: Set Overflow. but that's not the original name of the pin! it gets a little weird...
for the original name, you have to go back to the original 6502 schematic, where the pin is named C.P.S. what does that stand for? Chuck Peddle Special. Chuck was the main chip designer, and he wanted a really fast way to get data into the processor...
the clue is back in the hardware manual. this pin reaches deep within the bowels of the 6502 and flips on the overflow flag, and can be checked in a tight loop using a single fast (2 cycle) instruction, BVS, Branch if oVerflow Set.
the future I/O part is unknown and was probably never released, and nobody ever used the pin--except Commodore! they used it on the C64's 1541 disk drive: it signals the CPU that 8 bits have been written to the disk. (see baltissen.org/newhtm/1541a.h… for details.)
of special note: Sam was a rescue dog. if you're looking into getting a dog, please consider adopting a rescue dog.
thanks to @nwinograd for writing the original article about Sam at nathanwinograd.com/sam-the-most-f…. also a very special thanks to @team6502 for the utterly fascinating interviews and documents at team6502.org
