"Regulated" (as in RTOW/RTOM) has been the usual term since I were but a young lad and is more the British term, I suspect - "scheduled" is somewhat later and is likely to have originated in the US (?) .. or a least so it appears by my observation. I suggest "regulated" has a similar derivation based on predicted performance and compliance with a set of regulations.
... that didn't seem to have an answer that I could find written down
oh, brother .... get used to that little problem in this game. My first introduction was with one of the Oz majors at the time when I was an undergrad .. I was fortunate to be mentored for a vacation program by one of Oz's most experienced airline performance chaps and my interest developed from there.
If you have an interest in performance, there are a few engineering undergrad level aerodynamics/flight mechanics texts around which you would find useful. If you can get hold of the Boeing Performance Engineers Manual (used for their customer performance course) that is probably the single best text on the subject when it comes to airline-style performance work .. and only about 3-4 inches thick ..
Another source of excellent basic data is in the course notes for the various test pilot schools. The AGARD Flight Test Manual and ESDU Data Sheets, etc., hold a wealth of useful information both for the student and practitioner.