Maybe carols are secular?
And on the other thing, I don't know what you're talking about. Practically every time somebody knocks it's Pirates of Penzance.
We sing carols to each other; we sings hymns to God.
Carols are Holiday songs.
Not all carols are hymns, and not all hymns are carols, for the snark WAS a boojum, you see.
Carols are hymns.
Hymns which are not carols are to be sung in groups, reverently, earnestly.
Carols are to be sung in groups joyfully, merrily on holidays/holy days.
Those "Christmas carols" that have no reference to the birth of Christ, a la Jingle Bells, Frosty, Rudolph, etc. are all simply Christmas songs.