Understanding Area Palm stem thickness

[FloridaKeysGrower]

How does the stem (blue in photo) of an Areca Palm actually get thicker? Is that from the growth of new fronds from the center of the stalk? And the stem gets thicker to make room? OR is that from new growth from the sides that I cut off (circled in red) that seem to form their own sheath?

And how do the bamboo like rings come in to play as the plant matures?

I cut entire stalks and certain stems  because my end game is growing these things as tall and thick as possible. I have no ground so I’m planning to pot up as needed up to 23gallon diy planters (in a deep and tall 23 gallon trash bin with added drainage holes)(Currently in 7 gallon). 
 

Thank for any clues for how to help with this project. 

[Harry’s Palms]

As the palm grows , the demand for nutrients and water increase. The stem , or trunk , grows to supply that demand. How large it grows depends on the individual palm and growing conditions. The rings are witness to old frond bases.Your C. Lutescens  will be smaller in diameter than if it were grown in the ground it will also grow slower to some extent. It may or may not reach your desired height or size . Container gardening is not nearly as predictable as a ground garden. Harry

[aabell]

Almost everything you are looking at here, with the exception of the bottom 0.5" or so of rings at the base of each stem, are what you call the palm's crownshaft, not trunk or stem. The crownshaft (not all palms have this) is composed of extended leaf bases that wrap down and around the trunk as it is growing. When the oldest/lower leaves die, they shed off, and the trunk is slowly revealed as the palm grows. One ring on a palm's trunk = one old leaf that was shed. Your young palms are not really at the trunking stage yet, but the largest stems are close. 

 

[FloridaKeysGrower]

Wow thank you aabell and Harry’s Palms for helping me understand this process and helping me develop the correct vocabulary to describe it.