From LQWiki

ABEND stands for ABnormal END.

ABEND can mean abnormal termination (of software); crash; lossage. Derives from an error message on the IBM 360. Usually capitalized, but may appear as ‘abend’. Hackers will try to persuade you that ABEND is called abend because it is what system operators do to the machine late on Friday when they want to call it a day, and hence is from the German Abend = ‘Evening’.

It can also mean Absent By Enforced Net Deprivation — used in the subject lines of postings warning friends of an imminent loss of Internet access. (This can be because of computer downtime, loss of provider, moving or illness.) Variants of this also appear: ABVND = ‘Absent By Voluntary Net Deprivation’ and ABSEND = ‘Absent By Self-Enforced Net Deprivation’ have been sighted. This usage comes from the usenet newsgroup alt.callahans.

This article is based, in whole or in part, on entry or entries in the Jargon File.