Lisperati means lispers, lisp coders.
however, i just tried to google it for some definite confirmation. I think i read it in the 1990s from The Jargon File or LISP FAQ in newsgroup.
Strange, didn't find it after 5 min. Not in wikipedia lisp article. Was sure it's in jargon file or Online Free Computing Dictionary. Neither. comp.lang.lisp group search turned out 2 or so results other than lisperati.com (Conrad Barski, the LAND OF LISP book guy and alien lisp logo guy). Tried google group search 1990 to 2000, no result. (am pretty sure it's there, but google group search has been fucked since about 2005)
btw, emacsen is the hacker's jargon for the plural of emacs.
(thanks to Tim Bradshaw and Yuriv Khan for a correction.)