The first time I heard the word "abend", I asked the speaker what it meant. He couldn't really answer: "you know, abend!" Eventually I got the sense that it meant "crash", but it seemed like some crashes met his unarticulable criteria and some did not.
And, from the Jargon File, the joke was that this is what happened to jobs at the end of the day because the operators would shut off the computer before they went home at night, so it originates from the German Abend (evening).
