Here's an article about a study of why "nursery words" exist in so many languages. Nursery words are things like mama (English), papa (Italian), baba (Ukrainian), and titi (Hungarian).
The study examined brain scans of babies as they listened to various words: "Brain activity increased in the babies' temporal and left frontal areas whenever the repetitious words [baba or nana] were played. Words with non-adjacent repetitions ('bamuba' or 'napena') elicited no distinctive responses from the brain."
The experiments showed that "The brain areas that are responsible for language in an adult do not 'learn' how to process language during development, but rather, they are specialized — at least in part — to process language from the start."
My own $0.02 here is that this is just one aspect of the mind's penchant for pattern recognition. As we evolved, our minds were selected for their ability to recognize patterns in whatever we perceive. This study is a wonderful example of why - the newborn brain can recognize a pattern of repeated syllables (baba) but isn't yet sophisticated enough to recognize the repetition when there is noise in the signal (bamuba).
The infant brain is flooded with new inputs as it adapts to life outside the womb. With no context for any of it - with no existing mental model of the world - all of the sights, sounds, smells etc are essentially random noise. The baby has no frame of reference to distinguish one perception from another: at first, the mother and the father aren't any more noteworthy to a newborn than the janitor or photographer. The babe's brain takes its best shot at building symbols for all the things it sees, but as various symbols fail to re-occur, they wither and fade out. It is only the repetition of seeing the mother over and over again that reinforces that symbol in the brain and allows the baby's mind to say "this is not a random image I keep seeing".
Similarly, the baby has no instinctive way to know that a conversation between its parents is a type of sound any more relevant than the sound of a door closing or window opening. But the repetition of "parents talking" especially in concert with the repetition of seeing the parents over and over again lets the baby's brain start to recognize that the sounds are not random. From there, it's a short step to assigning meaning to some of those sounds - how natural that the first words a baby learns feature both the repetition of syllables ('mama') and an association to a highly non-random image (the mother's face.)
I wonder if you repeated the study, but instead of using repeated syllables (nursery words) you used repeated sound effects (a drum roll, maybe?) the same areas in the brain would fire. I don't know if there's anything magic about the fact that it is a word that the babies heard that matters - after all, baby animals learn to assign meaning to the sound of their parents (screeches, roars, hisses, etc) without speaking Italian.