Ethylene
In 1866, the German chemist August Wilhelm von Hofmann came up with a system for naming hydrocarbons. The suffixes -ane, -ene, -ine, -one, and -une were used to call the hydrocarbons with 0, 2, 4, 6, and 8 fewer hydrogen atoms than the alkane it came from.  Because of this system, ethylene became ethene.