The edge-of-the-screen trick is a very effective method for survival
in many computer games
. I read the word in The King's Quest Companion
many years ago, and has not, as of yet
, seen it any other places.
The trick to the trick is that in many computer games, monsters will not chase you off a screen and into the next. In some games, (Neverwinter Nights, Ancient Domains of Mystery and King's Quest IV comes to mind,) monsters will only chase you off the screen if they are very close to you when you leave. In both cases you can easily avoid dangerous encounters by leaving to the next screen.
Note that simply walking/running/swimming to the next screen is not the edge-of-the-screen trick. The edge-of-the-screen trick is to stick close to the edge of the screen so that when/if a monster appears you will have no trouble escaping with the aforementioned method before it reaches you. This is how you avoid loosing your magical mirror to the pesky dwarf in King's Quest I.