However, as it concerns manufactured products, it seems the first was from Honda, who released in 1977 a vehicle they called the Odyssey, essentially an "off-road" go-kart with a 250 cm3 two-stroke engine, single-seat, and a continuously variable automatic transmission (CVT).
The main differences to the traditional racing go-kart were a bigger size of tires (giving greater ground clearance and off-road traction) and a roll cage.
Changes were an improved roll cage, 350 cm3 engine with an electric starter, and a full front and back suspension system.
In addition to the increased engine size (a liquid-cooled 400 cm3 unit), it had its suspension improved to handle the extra load.
"Buggies" were originally made by converting existing vehicles (usually VWs, like the Volkswagen Beetle) and were usually intended for both on-road and off-road use (mainly on sand or beaches) and the majority still are.