Eagerness, n.
1. The state or quality of being eager; ardent desire. "The eagerness of love." Addison.
2. Tartness; sourness. [Obs.]
Syn. -- Ardor; vehemence; earnestness; impetuosity; heartiness; fervor; fervency; avidity; zeal; craving; heat; passion; greediness.
Shades of meaning
Fernald has no entry of its own for eagerness; he lists it under enthusiasm.
He lists it without comment; the entries above explain its neighbors.