See thread An Cronan Bais (The Death Croon) for a little on one example of a 'death croon'.

Almost any song can be pressed into service as a lullabye; chiefly pop songs nowadays, of course. Folk song collectors of the early C20 frequently got songs from middle- and upper-class informants; these had usually been learned in childhood from their nurses, and many had been used as lullabyes. Obviously not designed as such, they will often just have been whatever the nurserymaid happened to know, and the subject matter could be pretty disturbing: Francis Child, for example, described 'Long Lankin' as 'the terror of countless nurseries', and the version Sharp got from Sister Emma of Clewer has a short and repetitive melody with a rather hypnotic feel to it, though the sleep that followed might well have been troubled.

Bob Copper wrote of being sent to bed with the bloody images of 'Admiral Benbow' running in his mind. Though not directly hostile to an infant, the effect of some of those songs must have been quite traumatic. Songs that actually express direct hostility to the child would seem to have been more of a safety-valve for a tired and frustrated mother or nurse, sung to an infant too young to understand what it meant.