About a month ago, I heard my son (8 months at the time) saying "ma ma ma ma" several times, but he wasn't reaching for or even looking at his mother, just his bottle. My best guess is that he was trying to mimic Cookie Monster's "om nom nom nom" because he was hungry.

Kids around this age have an extremely limited vocabulary made up of simple sounds and few syllables. As such, they tend to overload certain words. The article noted that, for a child of that age, "mama" doesn't just mean mother, but several things associated with mother. Beyond that, "mama" might also mean something else that starts with an m (like "more"), or it might simply be babbling (my son currently says "da da da" to everything he touches.)