Uncouth means rough and lacking any polish of manner. Uncouth behaviour, an uncouth remark, thoroughly uncouth.
It is a class judgement as much as a description, which is why it now sounds slightly grand and old-fashioned. It describes manners rather than morals. Note that couth exists as a jokey back-formation meaning the opposite; and that uncouth originally meant unknown or unfamiliar — the strange became the crude, which is a common enough slide.
1adjectiveuncouthRough and lacking any polish of manner.
“His uncouth table manners, like chewing with his mouth open, shocked her parents.”
uncouth is a quality of roughness.
Old English uncuth meant unknown or unfamiliar, from un- plus cuth, known, the participle of cunnan, to know. Can and ken come from the same knowing.
Proto-Indo-European
*ǵneh₃-
Proto-Germanic
*unkunþaz — unknown
Proto-West Germanic
*unkunþ
Old English
uncūþ — unknown; unfamiliar; strange
Middle English
uncouth
English, today
uncouth
From Middle English uncouth, from Old English uncūþ (“unknown; unfamiliar; strange”), from Proto-West Germanic unkunþ, from Proto-Germanic unkunþaz (“unknown”), equivalent to un + couth. The modern pronunciation does not show, the usual development of the Middle English vowel from the Great Vowel Shift. It is usually explained as a pronunciation taken from Northern English dialects, which did not undergo the diphthongization of the vowel.
Etymology from Wiktionary, CC BY-SA