One may speak about anything on earth with fire, with enthusiasm, with ecstasy, but one only speaks about oneself with avidity.
-- Ivan Sergeevich Turgenev, "A Correspondence," Essential Turgenev
Come, walk up, and purchase with avidity, Overcome your diffidence and natural timidity!
-- William S. Gilbert, Arthur Seymour Sullivan, Patience; or, Bunthorne's Bride
Avidity appeared in English in the mid-1500s, originating from the French word avide, meaning "to crave, long for." The term adds a dimension of intensity to the "eagerness" with which it is often equated.