Annoying as it is (cause let's not kid ourselves, it is annoying! 😂) they almost always say dada first. It has to do with the way they develop and the D sound is the sound that is easier for them to make so they learn it first.
my baby said mama for a few weeks then dada for a few weeks and now says gaga lol
They usually don't say mamma until their a bit more independent. Apparently it's because they see us mums as an extension of themselves so don't need to say our names 🥹