periphrasis
A roundabout way of referring to something by means of several words instead of naming it directly in a single word or phrase. Commonly known as ‘circumlocution’, periphrasis is often used in euphemisms like passed away for ‘died’, but can have a more emphatic effect in poetry, as in the use of kennings. It was especially cultivated by 18th-century poets whose principle of decorum discouraged them from using commonplace words: thus fish were called the finny tribe, and in Robert Blair's poem ‘The Grave’ (1743) a telescope is the sight-invigorating tube. The 17th-century French fashion for préciositécultivated periphrasis to excess.
http://oxfordindex.oup.com/view/10.1093/oi/authority.20110803100317925