Douglas Harper's Etymology Dictionary
"small harpsichord," 1520s, evidently from virgin, but the connection is unclear, unless it means "an instrument played by girls."
Wiktionary
n. 1 A virginal, a musical instrument in the harpsichord family. 2 (plural of virginal English)Category:English plurals
Wikipedia
The virginals or virginal (the plural does not necessarily denote more than one instrument) is a keyboard instrument of the harpsichord family. It was popular in Europe during the late Renaissance and early baroque periods.
Usage examples of "virginals".
Some writer of music for the virginals, Tomkins or somebody, had spoken of producing a tiny sequence consisting of the King's Rouse, the King's Vomiting, the King's Rest.
Looking into her eyes, he said he was sadly discontent, that he had been relishing the thought of her company, that he had envisioned quiet evenings where he would read to her as she embroidered or that she would play for him on the virginals and sing or they could play music together.