'trihydric' originates from a modern English chemical formation combining the prefix 'tri-' (from Greek 'treis') and 'hydric' (from New Latin 'hydricus' ultimately from Greek 'hydor'), where 'tri-' meant 'three' and 'hydor' meant 'water' or 'hydrogen'.

'trihydric' changed from 19th-century chemical usage and related coinages in New Latin and French (for example forms like 'trihydricus' or French 'trihydrique') and eventually became the modern English word 'trihydric'.

Initially it described having 'three waters' or three hydrogen atoms in older chemical phrasing, but over time it evolved to mean 'having three replaceable hydrogen atoms or three hydroxyl groups' in modern chemical usage.