penetrate, clear, pierce, strike home, sit up (all night)
徹 centers on going all the way through something: penetrating, piercing, or striking home. It extends to doing something thoroughly, like sitting up all night, where you push through until the end.
徹 combines 彳 (movement) with a phonetic component that historically relates to piercing or passing through. The exact origin of the right side is uncertain, but the character consistently expresses thorough penetration.
The left side 彳 suggests movement, and the right side looks like a tool breaking through layers. Imagine a drill moving forward and piercing through a wall until it comes out the other side.
For テツ, picture a metal tets (鉄, てつ) rod penetrating a barrier: tets -> テツ, and the rod strikes home.
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thoroughness; completeness; consistency
thorough; exhaustive; complete
staying up all night
to penetrate; to sink in
cool-headed; level-headed; hard-headed
obstinate; stubborn; inflexible
accomplishment; realization; attainment; fulfillment; achievement
thoroughly; through and through; out and out; in every way; from beginning to end; from start to finish
stubborn and short-tempered
stubborn person; diehard
staying up all night three nights in a row; triple all-nighter
inconsistent; illogical; unconvincing; not thorough; indefinite; half-way
staying up all night two nights in a row; double all-nighter
doing mundane things properly and thoroughly; thoroughness in all things; attention to detail
carrying out one's original intention
making (something) known to everyone; publicizing as widely as possible; dissemination
to stay up all night; to sit up all night; to do something all night
attain divine enlightenment; perceive absolute truth; experience spiritual awakening
all-nighter; staying up all night
all-night karaoke