Not prepared to receive, or unavailable to, callers (or to a particular caller).
That is not at home; relating to the fact of being not at home.
A person who is not at home; a record (as made in the course of a survey, opinion poll, etc.) that nobody was at home.
Late 16th century; earliest use found in Thomas Lodge (1558–1625), author and physician. From not + at + home.