Warabe uta (童歌?) are traditional Japanese songs, similar to nursery rhymes. They are often sung as part of traditional children's games. They are described as a form of min'yo: traditional Japanese songs, usually sung without accompanying instruments.
The centuries-old lyrics are often incomprehensible to modern Japanese (especially to children who are singing it), and others can be quite sinister on close analysis. Like many of children's songs around the world, because people are used to them from an early age, they are often oblivious to the real meanings.