quiet
静 centers on stillness and absence of noise: a state of quiet, calm, or peace.
静 combines 青 (blue/green) and 争 (contend). The traditional form 靜 uses 爭, suggesting a phono-semantic origin where 青 contributes the sound and the idea of stillness contrasts with contention.
Blue (青) is a calm color, and when it overcomes contention (争), everything becomes quiet.
For セイ, imagine a quiet scene where you say 'say' nothing: say -> セイ, and the blue calm keeps everything still.
Shizuoka (city, prefecture)
quiet; silent
calmness; composure; coolness; serenity; presence of mind
quiet; calm; still
stillness
stillness; rest; being stationary; standing still; coming to a standstill
vein
rest; quiet; repose
silence; stillness; quietness
to quiet (a child, crowd, etc.); to quieten; to make quiet
calming down; settling down; quieting down; quietening down; subsiding; pacification; appeasement
settling down; quieting down; cooling down; cooling off
static electricity
static
state (of affairs); condition; developments; movements
stillness; silence; quiet; hush; calm; serenity
watchful waiting; careful supervision
quiet; still; calm
silent
to become quiet; to quiet down; to quieten down