Meaning

noun calm and unruffled self-assurance

noun the property of being moderately cold

noun fearless self-possession in the face of danger

originFrom Middle English colnes, colnesse, from Old English cōlnes, cœ̄lnes, cēlnes (“coolness; cool air, breeze”), from Proto-West Germanic *kōlinassī, equivalent to cool + -ness. Cognate with Middle High German kuolnisse, küelnisse (“cooling, coolness”).

Etymology from Wiktionary, CC BY-SA 3.0