From its earliest days, hardboiled fiction was published in and closely associated with so-called pulp magazines, most famously Black Mask under the editorship of Joseph T. Shaw. In its earliest uses in the late 1920s, "hardboiled" did not refer to a type of crime fiction; it meant the tough (cynical) attitude towards emotions triggered by violence.
Hardboiled writing is also associated with "noir fiction". Eddie Duggan discusses the similarities and differences between the two related forms in his 1999 article on pulp writer par excellence, Cornell Woolrich. In his full-length study of David Goodis, Jay Gertzman notes: "The best definition of hard boiled I know is that of critic Eddie Duggan. In noir, the primary focus is interior: psychic imbalance leading to self-hatred, aggression, sociopathy, or a compulsion to control those with whom one shares experiences. By contrast, hard boiled 'paints a backdrop of institutionalized social corruption'" 
Black Mask moved exclusively to publishing detective stories in 1933, and pulp's exclusive reference to crime fiction probably became fixed around that time, although it's impossible to pin down with precision. The hardboiled crime story became a staple of several pulp magazines in the 1930s; in addition to Black Mask, hardboiled crime fiction appeared in Dime Detective and Detective Fiction Weekly. Later, many hardboiled novels were published by houses specializing in paperback originals, also colloquially known as "pulps".
^Gertzman, J. A. (2018). Pulp According to David Goodis. Lutz, FL: Down & Out Books. p. 53.
^Sampson, Robert & Deandrea, William L. (Editor) (1994). "Pulps". Encyclopedia Mysteriosa. MacMillan. pp. 287-9. ISBN978-0-02-861678-0.CS1 maint: uses authors parameter (link) "Extremely tough, unsentimental and lethal, Everhard foreshadowed the hard-boiled characters of the following decade".
Mizejewski, Linda (2004). Hardboiled and High Heeled: The Woman Detective in Popular Culture. Routledge Chapman Hall. ISBN0-415-96970-0.
O'Brien, Geoffrey. "The Hardboiled Era: A Checklist, 1929-1958". miskatonic.org/rara-avis. A chronology of significant hardboiled novels, compiled by critic Geoffrey O'Brien for the 1981 edition of his Hardboiled America.