Ironically I was just looking at nslookup's man page[1] the other day and this bit of history is hinted at there:

    class=value

    Change the query class to one of:

    IN
        the Internet class
    CH
        the Chaos class
    HS
        the Hesiod class
    ANY
        wildcard

Man pages have amazing nuggets of history in them if one chooses to dig in!

[1] https://linux.die.net/man/1/nslookup