the.com/octane

means A measure of a fuel's ability to resist premature ignition under pressure in an engine's cylinder — the higher the number, the more compression it can take without knocking.

from From 'octane,' the hydrocarbon molecule built from eight carbon atoms (Greek 'okto,' eight — the same root giving us 'octagon' and 'October,' once the eighth Roman month). Chemists named the compound for its structure in the 1800s, but it entered everyday language once the octane rating scale was developed in the 1920s, using iso-octane as the high-resistance benchmark against which all gasoline is graded.