The neologism “psychobilly” did not originate with the Cramps, though it might not ever have made its way into the vernacular of music criticism without them. After relocating to New York City from Sacramento (via Akron, Ohio), the band, led by the husband-and-wife team (and only permanent members) Lux Interior and Poison Ivy, began promoting their shows with flyers promising an experience both “psychobilly” and “rock & roll voodoo” in nature. 
The former adjective appears to have been appropriated from a Wayne Kemp-penned song, “One Piece at a Time ,” which was a 1975 hit for Johnny Cash. The humorous single relates the story of a Kentucky-born transplant to the assembly lines of Detroit, who despairs of ever earning enough to buy for himself one of the elegant Cadillacs he helps manufacture. Inspired, perhaps, by his insider’s perspective that the most luxurious of vehicles is just a collection of discrete parts, he hits upon the idea to smuggle a car out of the plant – one piece at a time.
The process, which begins in 1949, takes just over two decades, and the resultant ride is a collage of a Cadillac components from nearly two dozen model years. Responding to the curiousity of fellow CBers (remember, this is now the ‘70s), this Frankenstein of auto parts (whose own handle is, suggestively, “Cotton Mouth”), names his custom car “the Psycho-Billy Cadillac.”  
The backstory of the word, combining a hillbilly protagonist with an outlaw spirit, a hot rod, and hints of drug culture, all as presented in a song popularized by a legend of Country music and a badass, to boot, is a perfect origin myth for the music later labled with it.
Though the Cramps themselves rejected the term as a categorization for their particular flavor of garage-rockabilly , the association with Johnny Cash resonates beyond this one borrowed term; a later possible homage reinforces the Cramps’ status as the ur-psychobilly band in an almost comically direct way:
In 1978, the Cramps seemingly one-upped the Man in Black’s legendary 1968 concert at Folsom Prison with a free performance at California’s Napa State Mental Hospital. In recent years, the hospital has become notorious for the violence committed among inmates interred through the California criminal courts . At the time, though, the hospital had no such reputation and a far smaller population of forensic patients, but the choice of venue was still a surprising and transgressive one: Rockabilly among the “psychos,” as it were.
The Cramps were touring Northern California at the time, and had teamed up with video-art pioneeers TargetVideo77, whose warehouse studio in San Francisco had become an epicenter of avant garde, hardcore punk, performance and video art. A videograper was on hand to document the Cramps’ performance - and that of that headliners, the Mutants – with a Sony Portapak, one of the earliest consumer-level, portable video cameras (Unfortunately, by the time the Mutants were ready to take the stage, available light was insufficient for the camera the capture the performance. There are unsubstantiated claims that TargetVideo has plans to attempt to correct that footage, though). 
The Cramps played their short set before an audience comprised of Target artists, members of the studio’s loyal punk-rock party crew and mental patients. One of the most compelling aspects of the documentation is the difficulty the viewer has in telling one from the other.
The twitching, jerking, lip-synching enthusisam, the audience competition for back-up-vocalist duties (or lead vocals in the presence of an unattended mic) and even the too-cool-for-this-shit reading of a tabloid (see 7:19) at the dancefloor’s edge will all be familiar to modern clubgoers.
The raw, unpolished, almost primitive nature of both the Cramps performance and TargetVideo’s video has an immediacy and ungainly appeal that transcends the details of their construction. They are, in their ways, beautiful, passionate and idiosyncratic – like a Caddy made of pilfered parts over a working lifetime.
Or as Lux exhorts while the opening chords of “The Way I Walk” are strummed, “Somebody told me you people are crazy but Im not so sure about that – you seem to be all right to me.”
 The Wild Wild World of The Cramps. Ian Johnston, Omnibus Press 1990
 YouTube video of “One Piece at a Time”
 Lyrics to “One Piece at a Time”
 Great picture of the Psycho-Billy Caddy
 Downey, Ryan J. “Psyched to Be Here.” Alternative Press, November 2004, 76-82
 Violence at Napa State hospital
 The Target Video Blog