初期 ex は en と呼ばれていた？

The Traditional Vi の ex_cmdsub.c より。

/*
 * z command; print windows of text in the file.
 *
 * If this seems unreasonably arcane, the reasons
 * are historical.  This is one of the first commands
 * added to the first ex (then called en) and the
 * number of facilities here were the major advantage
 * of en over ed since they allowed more use to be
 * made of fast terminals w/o typing .,.22p all the time.
 */

en というのは初めて聞いたなあ。

[追記]

So we modified em and created en. I don't know if there was an eo or an ep but finally there was ex.

http://www.theregister.co.uk/2003/09/11/bill_joys_greatest_gift/

em の由来は想像通り「ed で何でもできるのは神だけだ」ということから。

em - Editor for Mortals - since only immortals could use ed to do anything