lament, grieve
唏 centers on expressing sorrow vocally: lamenting or grieving, often with a sigh or cry.
唏 combines 口 (mouth) with 希, which likely contributes the sound and may suggest a drawn-out breath or sigh. The exact historical development is uncertain.
A mouth 口 beside 希, which looks like a person with arms raised in grief. Picture someone crying out with their mouth open, lamenting a loss.
For キ, imagine a key unlocking a flood of tears: key -> キ, and the mouth 口 wails in grief.