A rondel is a verse form originating in French lyrical poetry of the 14th century (closely related to the rondeau, as well as the rondelet).
[1] Specifically, the rondel refers to "a form with two rhymes, three stanzas, and a two-line refrain that repeats either two and a half or three times: ABba abAB abbaA(B).
Cocking wrote that "the reader who comes across a poem bearing the title rondel by Banville, Rollinat, Dobson or Bridges and is curious enough to look for a definition of this form is likely to be more confused than enlightened.
[4] Later, famed Middle English poet Geoffrey Chaucer would adapt the French Rondel to serve as the basis for The Knight's Tale.
Later, English poet and critic Algernon Charles Swinburne would devise the roundel, a form based on the rondeau rather than Chaucer's Rondel.