The word "capsule" (カプセル, kapuseru) is pretty established in Japan. There are capsule toy machines (also often called "gashapon" or "gacha" but those are respectively Bandai/Tomy trademarks). As another commenter pointed out there are capsule hotels; the working name for Pokémon was originally "Capsule Monsters".
I don't know that show but capsule hotels [0] are also a big thing in Japan, more widespread and probably more well-known than the capsule tower