The dot on a lowercase i or j is called a tittle.  Without the tittle, the word tittles and titties would be easily confused.  Thankfully, we don’t have to suffer that confusion.  It is believed that in the phrase “to a T,” meaning exactly or meticulously, the T is short for tittle. You would be incorrect to assume that titties may also derive from tittle, as a nipple is no more than a bodily tittle.  Wow, that sentence sounded like something out of a creepy Dr. Seuss book.

P.S. tit comes from teat.