A "perikope" in Greek is a section or segment of anything, including text. So I don't see why you shouldn't use it for chunks of Attic text as well as NT, even if that's not an established use. There's not really any other word you could use, except "chapter" perhaps (Latin caput; but Gk. kefalaion is more like a summary, giving the main points). Our "paragraph" derives from the Greek custom of marking off sections of text with a short horizontal line (the paragraphe or paragraphos) placed beneath the beginning of the line in which a section ended. They didn't start what we call paragraphs on a new line, but just ran the text on from beginning to end, with occasional punctuation; and they didn't really have chapters. The same goes for the NT texts, until people started dividing it up into chapters and verses.