The little dot above a lowercase "i" and "j" has a name — what is it?

The small dot above a lowercase i or j is called a tittle, a genuine typographic term rather than a joke. It exists mainly to help distinguish the letter from a plain vertical stroke in handwritten or early printed text, and it shares its Latin root with the word title, both descending from a word meaning a small mark or point.

A serif is something different, it refers to the small decorative strokes at the ends of letters in typefaces like Times New Roman, not a dot above a letter. An umlaut is different again, the two dots placed over certain vowels in languages like German to signal a change in pronunciation.

Because of this shared root, the old expression 'to a T' meaning exact and precise may actually descend from 'to a tittle,' suggesting the original phrase praised accuracy down to the smallest possible mark on a page.