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Maybe they called it 'thunderbolt' because of the dive limit?

It's dive acceleration not dive limit made P47 succesful in history.

It's totally useless for having 1 Mach dive limit when your enemy could outdive you with better acceleration within 0.7 Mach and pull to level run away. Even if you fly the same a/c 500m behind your wingman, you couldn't catch up him when following his dive, could you?

While both German fighters could break hard downwards, and leave all models of the Spitfire trailing[/B], no German piston-engined aircraft could out-dive the Thunderbolt.

Although SpitfireIX/XIV has the same dive limit(if not better than) as fw190A/bf109G, he couldn't over take Germans in a dive.

Speed and altitude records
The Spitfire Mk XI flown by Sqn. Ldr. Martindale, seen here after its flight on 27 April 1944 during which it was damaged achieving a true airspeed of 606 mph (975 km/h).Beginning in late 1943, high-speed diving trials were undertaken at Farnborough to investigate the handling characteristics of aircraft travelling at speeds near the sound barrier (i.e., the onset of compressibility effects). Because it had the highest limiting Mach number of any aircraft at that time, a Spitfire XI was chosen to take part in these trials. Due to the high altitudes necessary for these dives, a fully feathering Rotol propeller was fitted to prevent overspeeding. It was during these trials that EN409, flown by Squadron Leader J. R. Tobin, reached 606 mph (975 km/h, Mach 0.891) in a 45° dive. In April 1944, the same aircraft suffered engine failure in another dive while being flown by Squadron Leader Anthony F. Martindale, RAFVR, when the propeller and reduction gear broke off. Martindale successfully glided the Spitfire 20 mi (32 km) back to the airfield and landed safely.[120] Martindale was awarded the Air Force Cross for his exploits.[121]

A Spitfire was modified by the RAE for high speed testing of the stabilator (then known as the "flying tail") of the Miles M.52 supersonic research aircraft. RAE test pilot Eric Brown stated that he tested this successfully during October and November 1944, attaining Mach 0.86 in a dive.[122]

On 5 February 1952, a Spitfire 19 of 81 Squadron based at Kai Tek in Hong Kong reached probably the highest altitude ever achieved by a Spitfire. The pilot, Flight Lieutenant Ted Powles,[123] was on a routine flight to survey outside-air temperature and report on other meteorological conditions at various altitudes in preparation for a proposed new air service through the area. He climbed to 50,000 ft (15,240 m) indicated altitude, with a true altitude of 51,550 ft (15,712 m). The cabin pressure fell below a safe level and, in trying to reduce altitude, he entered an uncontrollable dive which shook the aircraft violently. He eventually regained control somewhere below 3,000 ft (900 m) and landed safely with no discernible damage to his aircraft. Evaluation of the recorded flight data suggested that, in the dive, he achieved a speed of 690 mph (1,110 km/h, Mach 0.96), which would have been the highest speed ever reached by a propeller-driven aircraft, but it has been speculated this figure resulted from inherent instrument errors.[120]

That any operational aircraft off the production line, cannons sprouting from its wings and warts and all, could readily be controlled at this speed when the early jet aircraft such as Meteors, Vampires, P-80s, etc, could not, was certainly extraordinary.—Jeffrey Quill

[124]The critical Mach number of the Spitfire's original elliptical wing was higher than the subsequently-used laminar-flow-section, straight-tapering-planform wing of the follow-on Supermarine Spiteful, Seafang and Attacker, illustrating that Reginald Mitchell's practical engineering approach to the problems of high-speed flight had paid off.[125]