Mus. [Obscurely f. It. quinto or L. quint-us fifth.] A group of five notes to be played in the time of four. (Stainer & Barrett, 1876). So Quintolet.

1

1884.  Grove, Dict. Mus., IV. 173. These groups, which are sometimes called quintolets, sextolets, etc. … always have their numbers written above them.

2