Calhoun is a city on the planet Xenex that shares the name of the Xenexian clan of Calhoun living there. Accordingly, the title "calhoun" is also used as the title for the clan leader (i.e. "Calhoun of the Calhoun"). As of the year 2354, D'ndai of Calhoun was the clan leader.
M'k'n'zy of Calhoun was a native of Calhoun, and adopted this as his surname after enrolling in Starfleet Academy. (NF novels: novel, House of Cards; NF - No Limits short story: "A Lady of Xenex")