"Just US/GB terminology." More like Just US/US terminology
"I always thought the term 'flightdeck' originated when B747 was introduced." Umm, why yes, you are correct.
Cockpit or Flight Deck?
The term "cockpit" originated from the ancient sport of cock fighting where two fighting cocks were placed in a depression, or pit, in the center of a small arena. The floor of the pit is below the floor level of the arena and a low fence surrounds the pit and projects a foot or so above the floor of the arena. Because of the similarity, the term was also applied to small boats in which the crew and passengers sat in a sunken area below the deck level protected from water flowing on the deck by a low fence-like barrier or coaming.
When airplanes arrived in the early 20th century and evolved to the point of having what we now call a fuselage, the well-established nautical term of "cockpit" was applied to the openings in the top of the fuselage where the pilot compartment was situated. As airplane designs evolved into the modern closed-cabin configurations, the aeronautical sense of the term "cockpit" took on a different meaning and was used to identify the pilots' station regardless of form or location.
"Cockpit" or "Control Cabin" was therefore used for the pilots' stations in early transport design groups up to the time of the 707/727/737 airplane programs. When the 747 Program came along, however, major discussions took place on what to call an area that included the Control Cabin as well as extra crew seats and a possible crew rest area with bunks. The name "Flight Deck" was decided upon which eventually became a standard in the industry.
It is interesting to note that contemporary Flight Deck control panels still refer to a "Cockpit Voice Recorder" and not a "Flight Deck Voice Recorder." Amazingly, the term "cockpit” still persists in the industry.