The first association many of us have to the word ‘popcorn’ is the crescendo of popping sound as the firestorm of kernels transforms into crunchy white fluffs. According to John Bartlett’s Dictionary of Americanisms, the word ‘popcorn’ comes “from the noise it makes on bursting open.”
However, the distinctive popping sound does not come from cracking the external kernel shell but from the steam release when it cracks.
Popcorn comes from a specific variety of corn with small, hard kernels. Water is trapped in each grain, so heating them at a high enough temperature turns moisture inside kernels into steam. Because the kernel’s outer shell is firm and almost unbreakable, the pressure builds up inside. The steam causes the kernel’s husk to burst, releasing the soft inner flake.
The popcorn’s white-yellowish look comes from the starch inside the corn kernel that expands due to high temperature.