Leeneia wrote that the book she was thinking of also included the tune later used for Good King Wenceslas, not that Personent Hodie were that tune.

"Men and boys" is a phrase from one of the English translations of Personent Hodie, though from the fourth stanza, and not the beginning of the song.

Third, it's true that Piae Cantiones being published in 1582 has the publishing date during Renaissance and not the Middle Age. But it is a collection of late medieval Latin songs.