Translation:Το ψηφίο μου!
I must have assumed it was the word for "vote", as in υποψήφιος (candidate/one who attains votes).
They're all derived from the Ancient Greek ψῆφος though, which is indeed 'vote'. I think ψῆφος implied some sort of pebble that was cast into boxes when votes were being held, which explains the link to 'digit'.
Single number and/or character. It doesn't have an an anatomical meaning, as far as I'm aware.