Gothabilly is an offshoot of rockabilly. The term was first used by a band called "The Cramps", even though they were more of a "surf rock sound". The term was popularized by a series of albums by Skully Records. The band is assosiated with gothic rock by their tendency to dress the part with fetish clothing and "outlandish makeup".
The Cramps (seen above) are actually quite popular in the subculture and have been a influential to the psychobilly genre as well.
Gothabilly music is really nothing more than a mix of the goth subculture and rockabilly music. It keeps the country and blues that influenced rockabilly but adds punk and goth rock. It has romantic, literary, occult, and religious themes.
The fashion is 1950s inspired with rockabilly, gothic,and retro rock n' roll. A typical Gothabilly wardrobe would include stylized flames, 50s tattoes imagery, animals prints, creeper shoes, cherries, polka dots, pencil skirts, fishnet stockings, high heels, silks, satins, lace, corsets, velvet, top hats, PVC,and leather.