Question: where did the saying keep calm and carry on originate
[{'answer': '1939', 'provenance': [{'wikipedia_id': '21875788', 'title': 'Keep Calm and Carry On', 'start_paragraph_id': 1, 'start_character': 86, 'end_paragraph_id': 1, 'end_character': 90, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'strengthen morale in the event of a wartime disaster'}, {'answer': "`` Home Publicity '' posters"}, {'provenance': [{'wikipedia_id': '21875788', 'title': 'Keep Calm and Carry On', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 679, 'bleu_score': 0.9831208473513011, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1979516385722823591}, 'section': 'Section::::History.:Design and production.\n'}]}]