Other forms: notaries public; notary publics
A notary public is someone who's authorized to put their official stamp on a legal document, like a will or a contract, certifying that you signed it.
In ancient Roman society, the role of scribes grew in prestige until these note-takers were promoted to being government officials. Their notes, or notae, inspired a new name for them: the Latin notarius, "shorthand writer or clerk," from which notary is derived. Today's notary public is an appointed state official who witnesses document signings, confirming the identity of the people signing and making sure they are signing willingly.