SUPEREROGATORY
excess, extra, redundant, spare, supererogatory, superfluous, supernumerary, surplus
(adjective) more than is needed, desired, or required; “trying to lose excess weight”; “found some extra change lying on the dresser”; “yet another book on heraldry might be thought redundant”; “skills made redundant by technological advance”; “sleeping in the spare room”; “supernumerary ornamentation”; “it was supererogatory of her to gloat”; “delete superfluous (or unnecessary) words”; “extra ribs as well as other supernumerary internal parts”; “surplus cheese distributed to the needy”
Source: WordNet® 3.1
Etymology
Adjective
supererogatory (comparative more supererogatory, superlative most supererogatory)
Pertaining to supererogation; doing more than is required, especially with reference to good works in Roman Catholicism
Source: Wiktionary
Su`per*e*rog"a*to*ry, a.
Definition: Performed to an extent not enjoined, or not required, by duty
or necessity; as, supererogatory services. Howell.
Source: Webster’s Unabridged Dictionary 1913 Edition