TARMACADAM

Today I met a person from central Pennsylvania who uses the word macadam instead of asphalt, and that term fascinated me since I never heard it before, so I decided to do some research. Apparently that's a thing throughout Appalachia and parts of Ohio (although many other places use it to specifically refer to a type of gravel), and it was first used in 1824. The word is named after a Scottish engineer called John McAdam, who invented a technique of layering small crushed stones that constitutes the road type. In 1902, that process was refined by adding tar, so the word tarmacadam was created, and that eventually became our word tarmac. Macadamization is also a word tracing back to the nineteenth century. Tarmac has been consistently increasing in usage, but the other two peaked around the 1910s.