The story
, the host of Major Bowes Amateur Hour which was broadcast on the radio in the US from 1934 to 1945]] Probably from the names of series of US radio and television programs such as Major Bowes Amateur Hour (broadcast on the radio 1934–1945) and The Original Amateur Hour (on the radio 1948–1952, and on television 1948–1970).
Etymology from Wiktionary, CC BY-SA 4.0.