Puzzle ZHHP 

Workings

Hint
Here are the last words of some of the carols, but not in order: head, king, afar, grown, dismay.

Answer
God rest you merry gentlemen, let nothing you dismay.
We three kings from Orient are, bearing gifts we traverse afar.
Ding dong merrily on high, in heaven the bells are ringing.
Once in royal David's city, stood a lowly cattle shed.
While shepherds watch their flocks at night all seated on the ground.
Away in a manger, no crib for a bed, the little lord Jesus lay down his sweet head.
Oh little town of Bethlehem how still we see thee lie.
Hark the herald angels sing, glory to the new born king.
O come, all ye faithful, joyful and triumphant, o come ye, o come ye to Bethlehem.
The holly and the ivy, when they are both full grown.