TSUMUGU · TOCFL 2 (est.) · 字
該
該 ＝ 言 ＋ 亥
ㄍㄞ · gāi
aux — should; the said, that
字源 FORM — what the parts do
亥聲hài — gives the sound
{g,k,h}IThài → gāi — the {g,k,h} crossing; tone shifts too
Words (言) that cover every item — the old sense is complete, all-included: 該備、該博. What the full account assigns to you is what you should do: 應該; the item already covered is 該 — the said one: 該公司. 亥 hài carries the sound, worn from h to g.
意 · Meanings
(本義)完備（該博）— complete, all-encompassing
→應該、活該— should — what falls to one常用
⇒該地、該公司— the said, the aforementioned
(本義) original meaning · → ⇒ each arrow = one more step of extension