A caudate sonnet is a longer version of a sonnet. It includes 14 lines written in the standard sonnet style, followed by a coda. The word "coda" comes from Latin, meaning "tail," which is where the name "caudate" is taken.

The form was first credited to Francesco Berni. However, Burchiello (1404–1449) used the same structure in over 150 of his sonnets more than 50 years before Berni was born. Burchiello’s work was well-known beyond Florence and the fifteenth century. In the sixteenth century, during the Italian Renaissance, several famous writers wrote about Burchiello, including Antonfrancesco Grazzini, Anton Francesco Doni, Angelo Colocci, and Tommaso Costo. Berni was not only familiar with Burchiello’s work but also admired it. Berni once wrote:

*If I had Burchiello’s wit, I would willingly write you a sonnet;
For never did I have a theme and subject more sweet, more pleasant, more beautiful.*

According to the Princeton Encyclopedia of Poetry, the caudate sonnet is often used for satire. One famous example is John Milton’s poem On the New Forcers of Conscience Under the Long Parliament.

Gerard Manley Hopkins used the form in a less satirical way in his poem That Nature is a Heraclitean Fire. This poem is part of a series in which Hopkins experimented with different sonnet styles. Unlike the curtal sonnet, a 10½-line form created by Hopkins that has the same proportions as a Petrarchan sonnet, his caudate sonnet is a full sonnet with no changes, but it includes six extra lines. Hopkins made the ending more impactful by continuing a sentence from the 14th line to the 15th.

Hopkins explored the idea of adding a coda in letters with Robert Bridges. Bridges shared with Hopkins the importance of Milton’s use of the form. Though the purpose of Hopkins’ example was different from Milton’s satirical style, the coda helped both poets create a more stable ending in their poems.