In a Nutshell
When learning to talk, babies indulge in a behavior known as “babble” (the creation of random sounds) that eventually evolves into “echolalia.” (the automatic repetition of sounds you hear). “Mama” or “mom” are almost universal across all of human speech for two very simple reasons: the sound is simple, and the enunciation mimics the mouth motion of suckling at a mother’s breast.
The Whole Bushel
Linguists have divided the pantheon of human speech into different categories based on what part of the mouth is involved. Two of the simplest forms of sound enunciation are “labials” and “wide vowel sounds.”
“Labials” are sounds made with the lips: “buh,” “puh,” and “muh.” Because the lips have so many nerve endings, rubbing them against each other his highly stimulating for an infant. “Wide vowel sounds” are common among infants for a similar reason: they’re just raw noise like “ahhh” and “uhhh,” making them extremely simple and satisfying sounds to play with.
But to fully understand why “mama” and “mom” are so universal, you need to focus on how you pronounce the word. If you say it out loud right now, you’ll begin by pressing your lips together, begin resonating in your throat, and then maintain that resonance as you abruptly open your mouth. This mimics the exact mouth motion an infant uses to suckle at his or her mother’s breast, making it the most natural sound and motion to associate with motherhood.