'subtropical' originates from Latin, specifically the word 'subtropicus,' where 'sub-' meant 'under' and 'tropicus' referred to the tropics.

'subtropicus' transformed into the French word 'subtropical,' and eventually became the modern English word 'subtropical' through Middle English.

Initially, it meant 'under the tropics,' but over time it evolved into its current meaning of 'relating to regions adjacent to the tropics.'