The actual props did not have "stun", "disrupt" and such markings on the controls. The scales were mere numbers.
I believe there's a Roddenberry quote somewhere in Whitfield's MAKING OF STAR TREK concerning the naming of the phasers—that they were so named because their output could be adjusted. They didn't want some technical expert pointing out that LASERS can't do all the stuff depicted in the show.
(Meanwhile the weapons in SPACE: 1999 were called "LASERS" from time to time, yet had a stun setting.)