I did not know this

The Christmas Carol Do You Hear What I Hear was written in the 1960s.  I always imagined it was written some time in a previous century, or was based on some old songs or poems from olden times.  Especially telling is the fact that it deals with sing-song stories about the Nativity event when most songs by then were about chestnuts, snowmen and reindeer. Anyway, interesting tidbit about one of my favorite Christmas Carols.  Bonus trivia: the ones who wrote it were the same who wrote Rain, Rain Go Away.  Another song I imagined to be hundreds of years old.