1) One should not give a name after someone who died young. In such a case, they
should add another name to his name, and the added name should be used as the
first name. Some say that one who died before the age of fifty is considered to
have died young. Others say that one who died before the age of sixty is
considered to have died young.
2) This rule does not apply to one who died a natural death. Even if he was young,
not old, a child may be named after him.
3) Even a person who died a natural death, if he died childless, a child should not
be named after him.
4) If a tzaddik was assassinated at a young age, some say that we may
nevertheless name a child after him, in view of the fact that he was a tzaddik.