It's perfectly normal for this to occur; when you login Terminal remotely bash does a reverse DNS lookup. It will only be the same if the hostname is not specified on the network you're connecting from and there is no reply from the DHCP server, or the reverse lookup against the remote DNS server fails to resolve.
You can easily over-ride the default setting by using this command in Terminal:
# sudo scutil --set HostName archos
You can check it by using:
# nslookup nn.nn.nn.nn
( or )
# host nn.nn.nn.nn
(where nn signifies your Mac's ip address)
