WHOWAS <nick> [limit] [server|nick]

WHOWAS will show you the last known host and whois
information for the specified nick.  Depending on the
number of times they have connected to the network, there
may be more than one listing for a specific user.

If a limit is specified, WHOWAS will not show more
than that many listings.

The third parameter allows querying another server.

The WHOWAS data will expire after time.