TSUMUGU · C1 (est.) · 字
鈍
鈍 ＝ 釒 ＋ 屯
ㄉㄨㄣˋ · dùn
adj — blunt, dull; slow-witted
字源 FORM — what the parts do
釒義the metal radical — a blade, a tool
屯聲tún — gives the sounda sprout pushing up against packed earth — held back, massed
ITtún → dùn — the t- voices to d-, the tone falls
The metal radical (釒) with 屯 tún for the sound — and 屯 itself is a sprout straining against hard ground, stalled. A blade that won't cut through: blunt, 鈍刀; then a mind that's slow, 遲鈍.
故事 STORY — a scene to remember it by
刀刃（釒）卷了口，砍在木頭上彈回來——鈍了。
The blade's edge (釒) has rolled over; it bounces off the wood instead of biting — gone blunt.
字源記憶法
意 · Meanings
(本義)鈍、不利— blunt, not sharp常用
→遲鈍— slow, dull-witted常用
→鈍角— an obtuse angle
(本義) original meaning · → ⇒ each arrow = one more step of extension
關 · Related
鋭ruìthe opposite — 鋭 is the keen edge, 鈍 the blunt one; both take the metal radical屯túnthe sound donor, bare — a sprout stalled against packed earth