In Welsh poetry, dyfalu is the piling on of comparisons, definition through conceit. The word also means “to guess” in Welsh, and many poems of dyfalu have an element of guesswork, a fanciful and riddling dimension. “The art of dyfalu, meaning “to describe” or “to deride,” rests in the intricate development of a series of images and extended metaphors which either celebrate or castigate a person, animal, or object,” the encyclopedia of Celtic Culture explains. Dafydd ap Gwilym’s poems to the mist and the wind are classic fourteenth-century examples.
That is from Edward Hirsch, A Poet’s Glossary, which I am quite enjoying. There is interesting material on every page and it is written with passion. A hendiatris is a “figure of speech in which three words are employed to express an idea, as in Thomas Jefferson’s tripartite motto for the Declaration of Independence: “Life, liberty, and the pursuit of happiness.”” When there are only two words so employed, it is of course a hendiadys.