quick, prompt
倏 centers on sudden speed: something happening quickly or promptly, with a sense of immediacy.
倏 combines 攸 (a shape associated with flowing or distant movement) with 犬 (dog), likely suggesting the swift movement of a dog. The exact historical development is uncertain.
A dog (犬) darts out from under a shelter (攸) with sudden speed: 倏 means quick and prompt.
For シュク, imagine a dog shaking off water with a quick shuck sound: shuck -> シュク, and the dog moves promptly.