urgent
絿 centers on a state of pressing need or tension: something urgent, severe, or demanding immediate action.
絿 combines 糸 (thread) with 求, which likely contributes the sound and may suggest a sense of pulling tight or urgency. The exact historical development is uncertain.
Thread 糸 pulled tight by a demanding hand 求: the tension makes the situation urgent.
For キュウ, imagine a thread pulled so tight it makes a high-pitched 'kyu' sound, like a string about to snap: kyu -> キュウ, and the urgency is in the tension.