late Middle English: from Latin fulminat- ‘struck by lightning’, from fulmen, fulmin- ‘lightning’. The earliest sense (derived from medieval Latin fulminare) was ‘denounce formally’, later ‘issue formal censures’ (originally said of the Pope). A sense ‘emit thunder and lightning’, based on the original Latin meaning, arose in the early 17th century, and hence ‘explode violently’ (late 17th century).