early death, calamity
夭 centers on a life cut short or a sudden, tragic misfortune: an early death or a calamity that strikes before its time.
夭 is a pictograph of a person with a tilted or bent head, suggesting a young life cut short or a calamitous event. The modern form retains the slanted top stroke over 大 (person).
The slanted top stroke 丿 looks like a head drooping over the body 大, like a young person cut down before their time. This image captures early death and sudden calamity.
For ヨウ, picture a young yo-yo snapping its string mid-spin, ending its motion abruptly: yo -> ヨウ, and the sudden stop mirrors an early death.