A tanka is a form of 5 line Japanese verse, using 31 syllables. The tanka is structured on the number of syllables in the verse using 5,7,5,7,7 syllables in the lines. There is also an English form of tanka, derived from the Japanese structure. Syllabic poetry isn't common in English, but is instead used as the rhythm structure for poetry. Old folk songs in all languages often have common rhythmic meters, and it's likely that they're derived from ancient verbal usage techniques. Poetry was also a common form of rote learning, using rhythm and rhyme to enforce memory.
Examples of Tanka: