The Old Mixer wrote:
^He said "in TOS"...but FWIW, I don't think that in TOS, it had even been established that the Enterprise was a "Constitution-class" vessel...the dedication plaque said "Starship Class".
You are quite correct. "Constitution Class" was mentioned in the script for "Space Seed" as one of the starship manuals Khan had been studying (along with the primary phaser schematic of a starship of a "Constitution Class").
was never referred to as a "Constitution Class" starship in TOS onscreen, and The Making of Star Trek
makes no reference to it either, but instead twice to "Enterprise Class" ("The Menagerie" suggested there are alphabetical class designations, which I believe is what the producers intended before Gene L. Coon introduced "Constitution Class" in the script for SS).
Essentially, "Constitution Class" was fanwank, but it appears Bjo Trimble, Greg Jein and Franz Joseph were so taken with the idea that this class designation stuck.
I still consider it erroneous (other than for NCC-1701-A), therefore
NCC = Not Constitution Class
(more in the Trek Tech section in a thread with the same title, the thread addressing the Constellation's registry and others)
P.S. "Connie" = nickname for the Lockheed Constellation
plane and the US Navy aircraft carrier USS Constellation