Definition:

tittle : the dot over i or j

Example Sentence:

In a handwritten business note, it's best to avoid smiley-face tittles.

Origin:

Tittle comes from the Latin titulus, which originally meant "title." Titulus came to refer to marks such as the abbreviated form of n written over a vowel (like the Spanish tilde, which indirectly got its name from titulus), and then to any mark above a letter.