One of the earliest 'high G' aircraft was Sopwith Pup, a 1916 vintage, canvas wing bi-plane with wooden frames. This aircraft could do a controlled bunt, with structural limits of -5G! It could also make a U-turn in less than 200 yards, building up almost 8 G in the process…
G-LOC was known as early as 1919, then called as 'fainting in the air'. and the
anti-G suits, which are still in use, date back to mid-1940's, Cotton's was air-filled (like the present ones) and Frank's was water filled.