don

don is a Noun

Definition:

[1] Sir; Mr; Signior; -- a title in Spain, formerly given to noblemen and gentlemen only, but now common to all classes. Don is used in Italy, though not so much as in Spain France talks of Dom Calmet, England of Dom Calmet, England of Dan Lydgate. Oliphant.

[2] A grand personage, or one making pretension to consequence; especially, the head of a college, or one of the fellows at the English universities. [Univ. Cant] "The great dons of wit." Dryden.