breve (n.)

c. 1300, "letter of authority" (see brief (n.)); mid-15c. as a medieval musical notation having one-half or one-third the duration of a "long" note (longa), from Latin breve (adj.) "short" in space or time (see brief (adj.)). In modern use it has the value of two whole notes and is the longest notation (though seldom used), which reverses the etymological sense. The grammatical curved line placed over a vowel to indicate "shortness" (1540s) is from the same source.