the word 'tannic' is a modern scientific adjective formed in english. its core, 'tann-', is derived from the old french 'tan', which referred to crushed oak bark used in the process of converting animal hides into leather. this term is believed to have celtic origins. the adjectival suffix '-ic', entering english via latin and ultimately from greek, is a standard linguistic tool for forming descriptive terms meaning 'of or pertaining to'. thus, 'tannic' literally means 'pertaining to tan (or tannin)', directly linking the ancient craft of leatherworking using bark to the modern chemical compound found in plants.

Structure: tann (substance) + ic (adjective suffix) tann (from french 'tan', referring to crushed oak bark used in leather making, of celtic origin) + ic (from latin '-icus', greek '-ikos', a suffix forming adjectives meaning 'of, pertaining to').