Superfluity, n.; pl. Superfluities.
Etymology: [L. superfluité, L. superfluitas. See Superfluous.]
1. A greater quantity than is wanted; superabundance; as, a superfluity of water; a superfluity of wealth. A quiet mediocrity is still to be preferred before a troubled superfluity. Suckling.
2. The state or quality of being superfluous; excess. "By a superfluity abominable." Chaucer.
3. Something beyond what is needed; something which serves for show or luxury.
Syn. -- Superabundance; excess; redundancy.
Shades of meaning
Fernald has no entry of its own for superfluity; he lists it under excess.
Where he writes about it:
Overplus and superabundance denote in the main a satisfactory, and superfluity an undesirable, excess; lavishness and profusion, a generous, bountiful, or amiable excess; as, a profusion of fair hair; lavishness of hospitality. — from excess