The story
This term apparently stems from manufacture in a gas producer.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A fuel gas that is manufactured from material such as coal or wood by partial combustion with air, usually modified by injection of water or steam to maintain a constant temperature and obtain a higher heat content gas by enrichment of air gas with hydrogen. Full definition →
This term apparently stems from manufacture in a gas producer.
Etymology from Wiktionary, CC BY-SA 4.0.