98.6 degrees Fahrenheit is traditionally given as the body temperature of a healthy adult human. This is, of course, nonsense.
Healthy humans generally have a body temperature between 97-99 °F, with a fever being anything over 100 °F (38 °C), and hypothermia being anything below 95 °F (35 °C).
The myth of 98.6 comes from the German doctor Carl Wunderlich, who measured the temperature of about 25,000 people and came up with an average of temperature of 98.6 °F. He published this is 1868, and it has stood as the God-given truth for over a hundred years, a strong testament to the urge of humans to seek out an over-precise number when a range would be much more correct.
98.6 is also a popular
rock-n-roll song written by
Tony Powers with music composed by
George Fischoff. It was recorded by
Keith, and released on his 1967 album
98.6/Ain't Gonna Lie. It reached Number 7 on the
Billboard chart (and number 24 on the
UK Singles Chart).
It is a light, cheerful pop tune, perhaps falling into the genre of bubblegum pop. It has been a staple of oldies stations for decades, and it is perhaps more well-known than its initial success in 1967 would have suggested -- and rightly so, despite somewhat cryptic lyrics. You can listen too it on YouTube, although other streaming sites are available.
It is perhaps worth noting that country singer Jill King also released a completely unrelated song called 98.6 on her 2003 album Jillbilly. While she is a fairly popular artist, this was not one of her more popular songs. YouTube link.