TECO
TECO is a powerful but complex text editor. It was first written 1962 for a PDP-1 at MIT's Research Laboratory of Electronics, and then ported to the Project MAC PDP-6 in 1964; it was for a long time the primary editor on ITS. EMACS was implemented using TECO's programming facilities.
The standalone PDP-6 version was modified in 1966 by Bob Clements, while installing the SAIL PDP-6, to run on the DEC Monitor. This evolved into DEC's "Standard TECO"; TECO was also re-written for many other computers, and spread fairly widely. A version was written for the PDP-11 (in MACRO-11) at MIT.
TECO humour
Dave Moon started a humorous term at MIT: 'TECO madness; a moment of convenience, a lifetime of regret'. (This is based on the tag-line from the old movie, Reefer Madness: "A moment of bliss; a lifetime of regret!"). Obviously Moon had written some complicated TECO command string to perform some complex change, and gotten it wrong - and it promptly ate something he had spent a considerable time typing in.