Nanook of the North
"Nanook of the North" was a nickname given to Odo by Vic Fontaine as a means of describing the Changeling's personality, which Vic compared to an icicle, adding, "Cool is one thing, but you're frozen solid."
Upon learning of Odo's affection for Kira Nerys in 2374, Vic attempted to lead Odo down a path that would allow him to thaw out a bit, so that Odo could allow his emotions come to the surface and thereby win Nerys' heart. (DS9: "His Way")
Vic's usage of the term "Nanook of the North" originates from the documentary film of the same name, which featured the life of an Inuit named 'Nanook' who lived in the Arctic of North America.