I know that it doesn't count as their first word, unless they know the meaning.

Since March, my daughter would say "mama" while crying when her dad was holding her, and reach out for me. She would only say it while crying, when someone else was holding her, and her reaching for me. In May, I went up the stairs, and she started to follow me and said "mama!".

Two weeks ago, she saw her dad's picture on the TV (a photo slideshow screen saver) and she yelled out "dada!". When he came home, she crawled into his lap and got an inch from his face and said "dada!".

A week ago, she has started babbling "dadadada" and "mamammaa", where as before, she would just say "mama" or "dada" and only while addressing/wanting us. Now, she babbles it randomly.

So my question is, does she know what these words mean? Or not, because she is now randomly babbling them (and still using them appropriately)