According to straightdope.com, Daniel Fahrenheit developed the thermometer, but asked a Danish astronomer Ole Romar what he should use for the scale. Romar thought 60 should be the boiling point of water and 0 should be "as cold as it ever got in Denmark" (because who likes negative numbers?)
That set the freezing point of water at 7.5 degrees. But Fahrenheit thought the fractions were crazy, so he multiplied everything by 4 to get 30 for freezing and 240 for boiling water.
Then, he multiplied the whole thing by 16/15ths for some unknown reason. Later calculations found water boiled at 212 and body temp was 98.6. And apparently, 0 is as cold as it ever gets in Denmark.
For More Information: