What does B movie mean?

B movie meaning in Etymology Dictionary

by 1939, frequently said to be so-called from becoming the 2nd, or encouraging, film in a double function. Some movie industry resources state it was so-called for being the second of this two movies significant studios generally speaking made in a year, in addition to one cast with less headline skill and released with less promotion. And very early consumption varies with grade-B film, recommending a perceived relationship with quality.