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In the publishing trade, a blurb is a testimonial to the book that is printed on the dust jacket. It is meant as an advertisement for the book. The origin of blurb is one of the more humorous etymologies.

Blurb was coined by the American humorist Gelett Burgess in 1907. According to his publisher, B.W. Huebsch, Burgess’s book, Are You a Bromide?, had been published and was selling well. At the annual trade association dinner that year the publisher distributed some five hundred copies of the book with a special jacket, as was the custom. It was also:

the common practise to print the picture of a damsel—languishing, heroic, or coquettish—anyhow, a damsel on the jacket of every novel.

Burgess provided a drawing of a particularly buxom and pulchritudinous blonde for the jacket and labeled her Miss Blinda Blurb. The name stuck, eventually including not only drawings of buxom women but also any excessive testimonial to the book.

From Burgess’s Burgess Unabridged, 1914:

Blurb 1. A flamboyant advertisement; an inspired testimonial. 2. Fulsome praise; a sound like a publisher...On the “jacket” of the “latest” fiction, we find the blurb; abounding in agile adjectives and adverbs, attesting that this book is the “sensation of the year.”

(Sources: Oxford English Dictionary, 2nd Edition; Mencken, The American Language, Supplement I)