'trichomatous' originates from New Latin, specifically the word 'trichomatus' (from Greek 'trichōma'), where 'trich-' meant 'hair' and '-oma' meant 'tumor or swelling', and the English suffix '-ous' (from Latin '-ōsus') denotes 'full of'.

'trichomatous' changed from New Latin 'trichomatus' (itself from Greek 'trichōma') through medical/Scientific Latin usage and eventually entered modern English as 'trichomatous'.

Initially it referred to a growth or tumor characterized by hair ('hairy tumor'), but over time it evolved to the broader descriptive sense 'having or covered with hair-like structures' used in botany and pathology.