Angry young man
Often applied to the British 'kitchen sink' playwrights of the 1950s. Also anyone, particularly young men obviously, who rails against the establishment.
The term was applied most notably to playwright John Osborne and it was from comments about his Look Back in Anger, first performed in 1956, that the phrase became known.
However, that wasn't its first use. In 1941, the writer Rebecca West used it in her Black lamb and grey falcon: the record of a journey through Yugoslavia in 1937:
"Their [the Dalmatians] instinct is to brace themselves against any central authority as if it were their enemy. The angry young men run about shouting."
West wasn't using the phrase in the quite specific way it became used in the 1950s. She was just referring to young men who were angry.
John Osborne's play Look Back in Anger was first performed in 1956. The term doesn't appear in the play but it was in the reporting of it later that it became known. In October 1957 George Fearon, Press Officer for the Royal Court Theatre, wrote this piece for the Daily Telegraph:
"I had read John Osborne's play. When I met the author I ventured to prophesy that his generation would praise his play while mine would, in general, dislike it... 'If this happens,' I told him, 'you would become known as the Angry Young Man.' In fact, we decided then and there that henceforth he was to be known as that."