The original COGPP was thought to simply be Diamond Peak, even in the case where Diamond is lower than Oregon Butte. In 2006 I pointed out that another peak in this county was probably, but not certainly, more prominent than Diamond Peak. In turn, Andy Martin located the then unnamed Prominencians Peak which was definitely more prominent than Diamond. John Roper quickly went back so as to be the first to summit this peak and thereby re-complete the WA COGPPs (his 1st of several re-completions). So in honor of the hobby of prominence and the folks who found this little peak and forced him to drive all the way back to the Blue Mtns to get it, John decided to name it Prominencians Peak. I believe this all happened during 2006.
Obviously the quirk of Diamond Peak's 6360+ contour means that we don't know the true COGPP to this day as it all depends on whether Diamond is higher than Oregon Butte and thereby the highest and also most prominent peak in the Blue Mtns.