Definition of "debugger"

6. Memorandum PDP-23, ID Invisible Debugger, August 20, 1964.

1965 January 15, J. B. Dennis, “Computer Research”, in Massachusetts Institute of Technology. Research Laboratory of Electronics. Quarterly Progress Report, no. 76‎, Cambridge, Massachusetts: Research Laboratory of Electronics (RLE) at the Massachusetts Institute of Technology (MIT), archived from the original on 2010-07-03, page 360

Invisible Debugger, commonly referred to as ID, a utility program in the PDP-1 time sharing system written to aid in the debugging of other programs. An advanced ID has been written (April, 1966) to allow all operations to be carried out either directly on drum fields or on running cores.

1966 May 20, MIT Electrical Engineering Department, chapter ID, in PDP-23-1‎, Cambridge, Massachusetts: Massachusetts Institute of Technology, archived from the original on 2011-02-18, page 1