protect, safeguard
怘 centers on guarding something valuable: protecting it from harm or keeping it safe.
怘 combines 古 (old) and 心 (heart/mind), but the exact historical development is uncertain. It may be a phono-semantic compound where 古 contributes the sound and 心 the idea of guarding with one's heart, but this is speculative.
An old (古) heart (心) that has seen many dangers knows how to protect and safeguard what matters.
For コ, imagine a small child (子, こ) being protected by an old, wise heart: 子 -> コ, and the old heart keeps the child safe.