'subcategory' is formed from the prefix 'sub-' meaning 'under' or 'below' and the word 'category', which comes from Greek 'katēgoria' meaning 'category' or 'class'.

'Subcategory' was formed in modern English by combining 'sub-' and 'category', which itself came from the Greek 'katēgoria' via Latin and French.

Initially, it meant 'a category under another category', and this meaning has remained unchanged in modern usage.