TSUMUGU · TOCFL 2 (est.) · 字
幹
幹 ＝ 倝 ＋ 干
ㄍㄢˋ · gàn
noun/verb — trunk, main part; to do, to manage
字源 FORM — what the parts do
倝聲gàn — gives the soundthe sun rising behind a banner; worn into the left side 龺 + 𠂉, hard to spot now
Tgān → gàn — tone settles late; same initial family
The old graph carries two tellings of who holds the sound. In one, 干 on the right — the pole — is itself the sound-bearer (干聲). In the other, the sound sits in 倝 gàn, a sun climbing behind a banner, worn into the left side until it is almost out of sight (the head graph 榦, 从木倝聲). Either way the word names the upright post you tie a wall-frame to (築牆耑木); from the post came the trunk (主幹), the backbone of a thing, and from there to do the main work: 幹事、能幹.
故事 STORY — a scene to remember it by
一根直木（干）立起來，牆就靠它撐——它是整面牆的主幹。
A straight post (干) stands; the wall leans on it — the post is the trunk that holds everything up.
字源記憶法
意 · Meanings
(本義)築牆的直木— the upright frame-post for a wall
→主幹、骨幹— trunk, backbone — the main part常用
⇒幹事、能幹— to do, to manage — to handle the main work常用
(本義) original meaning · → ⇒ each arrow = one more step of extension