Dennis Byron published an article about where the term "Business Process Management" comes from.? I think the difficulty with finding the roots of the term, however, are that the term BPM or "Business Process Management" is the coincidence of three very common words that have been in the lexicon for a very long time.
To me, I think the more interesting question is who started to apply the term BPM to the software they were building - or who started to write software to target the as-yet-non-existant BPM software market :) That would at least point toward who the early thought-leaders were in the software part of the BPM space.
Unfortunately it looks like his findings (based mostly on reader feedback and academic feedback) are somewhat inconclusive!? I guess we'll have to settle for waiting to find out who "wins" the BPM market instead.? It is taking a lot longer to play out than I anticipated when I got involved in the BPM market in 2003.