don 1 
(dŏn)
(dŏn)n.
1. Don (also dōn) Used as a courtesy title before the name of a man in a Spanish-speaking area.
2. Chiefly British
a. A head, tutor, or fellow at a college of Oxford or Cambridge.
b. A college or university professor.
3. The leader of an organized-crime family.
4. Archaic An important personage.
[Spanish dialectal and Italian, both from Latin dominus, lord; see dem- in the Appendix of Indo-European roots.]