Traumerei by Robert Schumann is from his larger work "Scenes From Childhood", written in 1838. It's possible Traumerei is one of the most misspelled piano solos...this is probably Schumann's most well known composition - simple and reflective; perfect as a lullaby.
Traumerei has no lyrics, to my knowledge. The melody spans a large range, slightly more than our national anthem, so it's unlikely to become a hit as a lullaby even if someone did put words to Schumann's music. Then again, who am I to say you can't sing the national anthem to your child as a lullaby?