Leo babbles "mom" and "mama" all the time. It's really just babbling at the ages that you mentioned. I don't actually remember how old Violet was when she said her first word, but it must have been somewhere around 11 months. Her first word was "kitty cat." By a year she had 3 words. I can't remember which ones, but her earliest words besides kitty cat were "up," "dada," and "that." She didn't say "mama" until somewhere around 16 months or so.