dying young
殀 centers on the tragedy of a life cut short: dying young, before reaching full maturity.
殀 combines 歹 (death) with 夭 (young, tender), suggesting the idea of dying while still young. The exact historical development is uncertain, but the component combination is consistent with the meaning.
The death radical 歹 beside 夭 (young) paints a stark picture: a young life cut short. Think of a tender sprout 夭 withering beside a coffin 歹.
For ヨウ, imagine a young person's life ending too soon, like a yo-yo that snaps and falls still: yo -> ヨウ, and the string breaks.