I always heard it as, "Feets don't fail me now!"

I always figured that, since the Chinese make all the chips, they were in a position to put anything they wanted directly into the hardware if they desired. Kinda makes you wonder about all that military hardware out there, doesn't it.

The story I heard is that it originated when computers had mechanical relays to act as logic gates. A moth became trapped under one of the relays causing the program to malfunction. Hence, the program had a bug (literally).