What was the name for illegal underground comics in the early 20th century?

Illegal underground comics in the early 20th century were often referred to as "Tijuana bibles" or "Eight-pagers." Other names for the comics include Tillie-and-Mac books, Jiggs-and-Maggie books, jo-jo books, bluesies, gray-backs and two-by-fours.

Tijuana bibles were published from the 1920s to the 1960s. The content of these books was of a sexual nature and prominently featured public figures and movie stars of the era. The cartoons were obscene parodies of popular comic strips of the day.

The books were sold under the counter in places where men tended to congregate. The name "Tijuana bible" was first noted in the 1940s, when it was rumored that the books were smuggled into California from Mexico.