It's called Boontling, and the back-country dialect has been spoken for 160 years or so in Boonville and the surrounding hamlets of California's Mendocino County. But because so little "bahl harpin'" (fluent speaking) is going on today, Boontling is "pikin' to the dusties," or dying, reports the San Francisco Chronicle. How little? Only 12 speakers are left. "It's already just about gone, and it's just us old-timers that really speak it now," says Wes Smoot. "When we die, that's it."
Nobody's exactly sure how or why Boontling started, but it was once used in local schools—and a speaker once turned up on Johnny Carson's Tonight Show. "I never found another language as extensive as Boontling anywhere," says a Cal State linguist who wrote a book about it. The Chronicle provides one example of how a word came to be: A phone booth turned into a "buckey walter" because someone named Walter once had the area's first phone, and he charged people a nickel, called a buckeye back then, to make calls. Click for the full story, which has more translations, including "applehead" for girlfriend.