The spinet is a member of the harpsichord family. It is a keyboard instrument with plucked strings like the virginal, but varies from that instrument in that the sound box is not rectangular but sort of wing-shaped, rather like the modern grand piano. The strings lie at 45 degrees to the keyboard, allowing the bass strings to be longer thus giving the instrument greater sonority. Its shape gave rise to its being referred to occasionally as the “couched harp”.
The term may have derived from an Italian inventor, Spinnetti, or from the “spines” or quills that act as plectra. It flourished for the century between the late 17th and about 1800, with instruments still being made at that later time. There were well known spinet makers in colonial America.
For the mechanics of the instrument, see virginal.
Reference: “The Grove Concise Dictionary of Music”