1911 Encyclopædia Britannica/Lullaby

LULLABY, a cradle-song, a song sung to children to “lull” them to sleep; the melody being styled in Fr. berceuse and in Ger. Wiegenlied. “Lull,” cf. Swed. lulla, Du. lullen, &c., is of echoic or onomatopoeic origin, cf. Lat. lallare, to chatter.