Definition of "nymphet"

Of the nymphets sporting there In Wyrrall, and in Delamere.

1612 Michael Drayton, Poly-Olbion I. xi. Argt. 171

[…] the fey grace, the elusive, shifty, soul-shattering, insidious charm that separates the nymphet from such coevals of hers […]

1955, Vladimir Nabokov, Lolita, 1st American edition, New York, N.Y.: G[eorge] P[almer] Putnam’s Sons, published August 1958, part 1, page 19