Motherese
I learned a cool word in my Acquisition of Language class this week: motherese, speech that is high-pitched, repetitive, simple, and typically directed at young children.
I found a message from Steven Pinker about the term (and 8 synonyms or related terms). He also talks about an early version of the American Heritage Dictionary's definition for "child-directed speech".
Pinker prefers the term "child-directed speech", saying it is the most transparent. I prefer "motherese" because it is clearly a term and therefore must refer to some phenomenon worth naming. "Child-directed speech" could be mistaken to mean "any speech directed at a child". "Child-directed speech" tries to be more inclusive, but still misses the fact that people also use it when talking to cats. I also prefer "motherese" because it's short, easy to remember, and slightly silly.