Well, Spanish is a Romance language[1]. ‘Mamma’ is Latin for ‘breast’, so that makes sense. It’s where words like ‘mammal’ and ‘mammogram’ come from.

http://en.wikipedia.org/wiki/File:LatinEuropeans.png

Even more interestingly, "ma(ma)" means breast too in the dialect of my home town which locates at the central part of China.

In baby-Turkish "mama" means meal. And "meme" means breast.