From the article:
Generator gas has been used extensively since the middle of the 19th Century in the iron working industry for the firing of furnaces. A Swedish design which first attracted attention was the gas generator invented by Gustaf Ekman at Lesjofors and named "Ekman's Coal Shaft Furnace." It was described in Jernkontorets Annaler 1843 (Annals of the Swedish Ironmasters Association, 1843). The "downdraft principle" (gases passing down through the firebed) of this generator is, on the whole, the same as that used for most gas generators for fueling engines. The first proposal for the use of generator gas for engines appeared in 1877 and the engine was run for the first time around 1881. It was used for stationary operation, and because the gas is sucked by the engine through the generator, the gas was usually called "suction gas." The first gas generator specifically constructed for stationary engine operation did not come into existence until the beginning of the 20th Century. Something similar, however, was described in an English patent as early as 1859.
With the outbreak of war in 1939, the use of generator gas for vehicular operation increased, and the head of the Swedish Board of Trade, Axel J. Enstrom, proposed the Swedish name "GENGAS," which soon was accepted in this field. Gas for firing industrial furnaces, however, is still usually called generator gas.
Not until around 1920 were there portable gas generators worth mentioning which could be used for motor vehicles although experiments had been carried out much earlier. At this time, portable gas generators were attached to trucks as well as to tractors. There was interest in France in this development, and the firm of Panhard &: Lavassor manufactured the first gas generator for practical use. Another French design was the Gohin-generator, which can be considered the forerunner of generators not enclosed in brick and with water vapor added. In Germany there was also great interest in generator gas operation; the best known is Imbert's gas generator for wood.