An Etymological Dictionary of the German Language/Annotated/frohlocken

by Friedrich Kluge

frohlocken, verb, ‘to exult, triumph, shout for joy,’ from Middle High German vrôlocken (rare), ‘jubilate’; according to Middle High German vrô-sanc, ‘song of joy, hallelujah,’ probably a corruption of an earlier form, frôleichen; Old High German and Middle High German *vrô-leich would be also literally ‘song of joy.’ English to frolic is derived from Dutch vrolijk, ‘joyous.’