Phrases of apparent nonsense in refrains (Lay the bent to the bonny broom?), and syllables such as fa la la, familiar from the Christmas carol "Deck the Halls with Boughs of Holly", have given rise to much speculation. Some[who?] believe that the traditional refrain Hob a derry down O encountered in some English folksongs is in fact an ancient Celtic phrase meaning "dance around the oak tree." These suggestions remain controversial.[citation needed]