plug up, obstruct
窒 centers on blocking passage: plugging up an opening or obstructing flow so that nothing can get through.
窒 combines 穴 (hole, cavity) with 至, which likely contributes the sound. The idea is a hole being stopped up or blocked.
A hole (穴) is stopped up when something reaches (至) it and blocks the opening. Picture a cork reaching a bottle's hole and plugging it tightly.
For チツ, imagine a blocked pipe that finally clears with a sharp 'cheats!' sound as the obstruction is forced out: cheats -> チツ.
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nitrogen (N)
suffocation; choking; asphyxia
nitridization; nitriding
dinitrogen monoxide; nitrous oxide
nitric monoxide
nitrogen dioxide
nitrous oxide (N2O)
molecular nitrogen
liquid nitrogen
gallium nitride
silicon nitride
boron nitride
nitride
blocked
choking gas
suffocating; asphyxiating
death by suffocation; death by choking
death from suffocation
nitrogen narcosis
nitrogen metabolism