Recall reading somewhere a description by Julius Caesar of the Celts(?) as being fast talking, often through gestures and half words. And often saying the opposite of what was intended. Like to find the exact quote and reference to that passage.
I think you're recalling a passage from Diodorus Siculus' The Library of History, Book V:
31 1 The Gauls are terrifying in aspect and their voices are deep and altogether harsh; when they meet together they converse with few words and in riddles, hinting darkly at things for the most part and using one word when they mean another; and they like to talk in superlatives, to the end that they may extol themselves and depreciate all other men.
Or else the enigmatical language of Druids in Diogenes Laertius' Lives and Opinions of Eminent Philosophers, which I've seen translated as riddles before:
§5. But they who say that philosophy had its rise among the barbarians, give also an account of the different systems prevailing among the various tribes. And they say that the Gymnosophists and the Druids philosophize, delivering their apophthegmns in enigmatical language, bidding men worship the gods and do no evil, and practise manly virtue.