Mentioned in The Last Continent, a well-known, but not terribly bright, explorer, who spent many years looking for XXXX, and never found it. According to the Dean of Unseen University, he once got lost in his own bedroom (in the wardrobe), though this might be an exaggeration. (or he'd heard about Narnia and was exploring likely possibilities).
He is understood to have spent several years going round and round in circles in the Circle Sea, just out of sight of land, under the mistaken impression that he was circumferentially navigating the Disc. He returned to Ankh-Morpork claiming to have proven that the Disc had a circumference of several million miles...
A fuller biography of Sir Roderick is given in the pamphlet accompanying The Discworld Mapp. The son of Major General Sir Ruthven Purdeigh, he was educated at Thrasher's School in Pseudopolis, and then at the prestigious Military Academy in Sto Lat. His first posting on passing out was to the Quirm Lancers, followed by promotion to the 35th Llamedosian Foot, where his immediate commander was Lord Rust. Owing to an administrative error, he was promoted to Colonel and sent to command the Royal Sto Plains Riflers, his father's old regiment. Purdeigh finished his Army service as Major General, being so promoted on the death of General the Duke of Eorle.
He left the army and published an autobiographical account of his military service, On The Use of Pliers in Warfare, Boots and Teeth: A Soldier's Life.
He then started his spectacularly unsuccessful exploring career as detailed above, meeting an untimely end in Bhangbhangduc at the hands of the natives. We know that Purdeigh was somewhat intolerant of untidy lazy slackers and foreigners, believing any little difficulties could be resolved by a few prods of the blunt end of his walking-stick to get them to shape up and show some backbone. As his last, sadly unfinished, book, The Man of the Woods, relates, Purdeigh was so incensed at the comportment of a group of red-haired slovenly rascals that he resolved to teach them a jolly good lesson with the said walking-stick.
We know today he had not encountered men, so much as the great ape, Pongo Pongo. Whoops. He may not have thought to use the M - Word, but in the circumstances this would have added insult to injury. The end result was the same, anyway.
The Malay words orang-utan simply mean Man of the Woods...
Another explorer who went round and round in circles just out of sight of land was the second Elizabethan incarnation of Edmund Blackadder (Rowan Atkinson) who, seeking to emulate Sir Francis Drake and regain prestige with Queenie, made the error of engaging the most incompetent ship's captain he could find (played by Tom Baker). He got no further than describing very big circles in the English Channel out of sight of either England or France. For quite some time.
Purdey's are a seriously upscale manufacturer of bespoke shotguns, established in London. The cost of a brace of guns is about the same as your investment in a new Rangerover to go to shooting meets in. Roderick's mother's maiden name is Burberry. Burberry are manufaturers of very exclusive - and expensive - clothing befitting the huntin', shootin', and fishin' set (despite an association with fashion and statuse-conscious hooligans).