Erethism or erethism mercurialis is a neurological disorder which affects the whole central nervous system, as well as a symptom complex derived from mercury poisoning.
 This is also sometimes known as the mad hatter disease.
 Historically, this was common among old England felt-hatmakers who used mercury to stabilize the wool in a process called felting, where hair was cut from a pelt of an animal such as a rabbit.
 The industrial workers were exposed to the mercury vapors, giving rise to the expression “mad as a hatter.”
 Some believe that the character the Mad Hatter in Lewis Carroll's Alice in Wonderland is an example of someone suffering from erethism, but the origin of this account is unclear.
 The character was almost certainly based on Theophilus Carter, an eccentric furniture dealer who was well known to Carroll.
Rules of origin are used to determine the country of origin of a product for purposes of international trade.
 There are two common types of rules of origin depending upon application, the preferential and non-preferential rules of origin (19 CFR 102).
 The exact rules vary from country to country, from agreement to agreement.
As volunteers clean up after a huge outdoor rock concert in Yorkshire in 1969, they discover the body of a young woman wrapped in a sleeping bag.
 She has been brutally murdered.
 The detective assigned to the case, Stanley Chadwick, is a hard-headed, strait-laced veteran of the Second World War.
 He could not have less in common with - or less regard for - young, disrespectful, long-haired hippies, smoking marijuana and listening to the pulsing sounds of rock and roll.
 But he has a murder to solve, and it looks as if the victim was somehow associated with the up-and-coming psychedelic pastoral band the Mad Hatters.
 In the present, Inspector Alan Banks is investigating the murder of a freelance music journalist who was working on a feature about the Mad Hatters for MOJO magazine.
 This is not the first time that the Mad Hatters, now aging rock superstars, have been brushed by tragedy.
 Banks finds he has to delve into the past to find out exactly what hornets' nest the journalist inadvertently stirred up.
Douglas Jack Agu (born 19 August 1989), better known by his stage name Runtown, is a Nigerian singer, songwriter and producer.
 He has a diverse musical style mix of hip-hop, R&B, reggae and rap.
 After moving to Lagos from Enugu State with Phyno in 2007, he started doing underground collaborations with artists like J-Martins and Timaya.
 In 2008, he partnered with Phyno to form a record label called Penthauz during which he released his first two singles: "Party Like It's 1980" and "Activity Pikin".
 He collaborated with Davido on his song "Gallardo", which brought him more attention.
 Few months later, he signed a multi-million Naira contract with Eric-Manny Entertainment owned by Prince Okwudili Umenyiora, the C.E.O of Dilly Motors.
Mad scientist (also mad doctor or mad professor) is a caricature of a scientist who is described as "mad" or "insane" owing to a combination of unusual or unsettling personality traits and the unabashedly ambitious, taboo and/or hubristic nature of their experiments.
 As a motif in fiction, the mad scientist may be villainous (evil genius) or antagonistic, benign or neutral; may be insane, eccentric, or clumsy; and often works with fictional technology or fails to recognize or value common human objections to attempting to play God.
 Some may have benevolent or good-spirited intentions, even if their actions are dangerous or questionable, which can make them accidental villains.
Chen ( ) () is one of the most common East Asian surnames of Chinese origin.
 It ranks as the 5th most common surname in China as of 2007 and the most common surname in Singapore (2000) and Taiwan (2010).
 Chen is also the most common family name in Guangdong, Zhejiang, Fujian, Hong Kong (spelled Chan in Hong Kong and Macau).
 It is the most common surname in Xiamen, the ancestral hometown of many overseas Hoklo.
 Besides 陳/陈, an uncommon Chinese surname 諶/谌 is also romanized as Chen.
Mad River Road was the first overland route between Dayton, Ohio and Cincinnati, Ohio.
 It was cut by Daniel C. Cooper in 1795 to provide access to the new town of Dayton and the "Mad River Country" northeast and north of Dayton.
 It was located at the mouth of the Mad River in the Symmes Purchase.
 The survey, entered into the record by Cooper and Dr. John Hole, extended Harmer's Trace north from near Cunningham's Station on the Mill Creek to the mouth of the Mad River, establishing the earliest road between Cincinnati and Dayton.
 Cooper, a surveyor and miller, was instrumental in the early settlement of Dayton, and Dr. Hole, the first physician in Montgomery County, established his cabin in 1796 near the now-extinct town of Woodburne on Mad River Road.
Country of origin (COO), is the country of manufacture, production, or growth where an article or product comes from.
 There are differing rules of origin under various national laws and international treaties.
 Country of origin labelling is also known as "place-based branding", the "made-in image" or the "nationality bias."
 In some regions or industries, country of origin labelling may adopt unique local terms such as terroir used to describe wine appellations based on the specific region where grapes are grown and wine manufactured.
"Mad Over You" is a song by Nigerian singer Runtown.
 Released on November 4, 2016, the song was primarily produced by Del B, with production assistance from Runtown and T-Spize.
 Described as a love-themed ballad, "Mad Over You" is a blend of Ghanaian highlife and R&B.
 It debuted at number 38 on the "Billboard" Twitter Top Tracks chart, marking the singer's first appearance on the US-based chart.
 As of March 2017, "Mad Over You" garnered over 2 million streams on the streaming media service Spotify.
A homeland ( "country of origin" and native land) is the concept of the place (cultural geography) with which an ethnic group holds a long history and a deep cultural association – the country in which a particular national identity began.
 As a common noun, homeland, it simply connotes the country of one's origin.
 When used as a proper noun, the Homeland, as well as its equivalents in other languages, often have ethnic nationalist connotations.
 A homeland may also be referred to as a "fatherland", a "motherland", or a "mother country", depending on the culture and language of the nationality in question.

Question: What country of origin does Mad Over You and Runtown have in common?
Answer: Nigerian