The Jargon File (version 4.4.7, 29 Dec 2003):
amp off vt. [Purdue] To run in background. From the Unix shell ?&? operator.The Free On-line Dictionary of Computing (30 December 2018):
amp off(Purdue) To run in background. From the Unix shell "&" (ampersand) operator. [Jargon File] (1995-11-14)