The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: Of or relating to the musical plagal mode on A, which uses the diatonic octave species from E to the E an octave above, divided by the final into a second-species fourth (semitone–tone–tone) plus a first-species fifth (tone–semitone–tone–tone): E F G A + A B C D E. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.