The name L’Homme Armé derives from a melody that probably dates to the beginning of the 15th century and has rather mysterious origins. This melody was used from the mid 15th cent. to the beginning of the 17th cent. as cantus firmus of more than 30 polyphonic masses.
“No one knows how and why the melody l’Homme armé became the basis of so many masterpieces of Renaissance polyphony. We do not even know what kind of melody it is. It is generally considered a melody of the people which was also very popular and that was widely know orally. Another theory though, states that it originated as tenor of a polyphonic prototype, maybe a court song from Bourgogne. Just as mysterious is the meaning of the text. Who is this “armed man?”
the candiates that have been considered are Henry V of England (who defeated the French at Agincourt in 1415), Charles VII of France (the Victorious who reigned from 1422 to 1461) and Charles the Temerarious, the last Duke of Burgundy.” (Taruskin 1980)