lull·a·by 
(lŭlə-bī′)
(lŭlə-bī′)n. pl. lull·a·bies
A soothing song with which to lull a child to sleep.
tr.v. lull·a·bied, lull·a·by·ing, lull·a·bies
To quiet with or as if with a lullaby.
[Obsolete lulla, word used in lullabies (from Middle English lullai, from lullen, to lull; see LULL) + BYE2.]