'minor' originates from Latin, specifically the word 'minor', where it meant 'smaller' (comparative of 'parvus').

'minor' passed into Old French as 'mineur' and Middle English as 'minour' (or 'minor'), eventually becoming the modern English 'minor'.

Initially it meant 'smaller' in a physical or relative sense, and over time it developed senses of 'less important' and specialized noun senses such as 'a person under full legal age' and 'a secondary academic subject'.