This is a delightfully imitative word, that rolls swaggeringly off the tongue, like the boastful or inflated talk or behaviour that it describes. It was created from Rodomont, the name of the boastful Saracen king of Algiers, in two famous Italian romantic epics, Orlando Innamorato of 1485 by Count Matteo Boiardo, and the sequel of 1516, Orlando Furioso by Ludovico Ariosto.
English borrowed the word rodomont in the sixteenth century as a way to describe an extravagant boaster or braggart. Our form appeared in the following century. At first it meant a single brag or boastful act, so that one could speak in the plural of rodomontades. In that form, the first known user was John Donne, in 1612: “Challengers cartells, full of Rodomontades.” Later it became both an adjective and a verb and a mass noun that refers to the whole business of making your point by laying it on rather too thick.
In that sense, it turns up in many works of literature, including The Tenant of Wildfell Hall by Anne Brontë: ”She knows what she's about; but he, poor fool, deludes himself with the notion that she'll make him a good wife, and because she has amused him with some rodomontade about despising rank and wealth in matters of love and marriage, he flatters himself that she's devotedly attached to him.”