The cork rump apparently became fashionable around 1770 as a means of extending a lady's backside to accentuate the waist.

The following story appeared in the Morning Post on 4 October, 1785:

"As much raillery has been levelled against the wearing of cork rumps, we shall insert the following most extraordinary fact in order to prove, that one of a good size is equal to a cork jacket, in accidents by water — a few days ago, a lady with an immense circumference of bottom, as she was stepping into a boat, at Blackfriar's Bridge, by the awkwardness of the waterman, in handing her off the Stairs, lost her footing, and tumbled into the Thames, but, instead of sinking, to the surprise of every body, from her hips up she appeared above water; all the boats immediately put out after her; but the wind and tide both going strongly down the river, which circumstance, added to an immense parachute hat she had on, acting as a sail, there was no overtaking her; in this exceedingly perilous state, the poor lady proceeded like a mermaid, till the alarm became so general on the river, that the combined fleets of the Old Swan, and Tower Stairs, put out all the Navies, and luckily meeting her as she passed London Bridge, towed her safely into Billingsgate; but her fright did not end here, for as she was stricken in years, and her dip in the Thames having restored her shrivelled countenance to its native sallow, the ladies of Billingsgate, with one united voice, pronounced her a witch.  Nor could she have escaped their fury, if she had not proved, to the satisfaction of these conscientious matrons, that it was not to the Devil but to a cork rump that she owed her safety."