The word "doth" is an archaic form of the verb "does." It is primarily used in poetry and in Shakespearean plays as a means of indicating the third person singular of the verb "do."
"Doth" originates from Old English "dōþ," which is a form of the verb "do." It is an example of how English has evolved over centuries, and it has largely fallen out of everyday use, retained mainly in literary contexts.