Definition:

tittle : the dot over i or j

Example Sentence:

Make sure you tittle your i’s and cross your t’s.

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.

Source: merriam-webster.com