Question: where did the phrase when pigs fly come from
[{'answer': 'Scottish proverb', 'provenance': [{'wikipedia_id': '21304262', 'title': 'When pigs fly', 'start_paragraph_id': 11, 'start_character': 53, 'end_paragraph_id': 11, 'end_character': 69, 'bleu_score': 1.0, 'section': 'Section::::Meaning.\n'}]}, {'provenance': [{'wikipedia_id': '21304262', 'title': 'When pigs fly', 'start_paragraph_id': 11, 'start_character': 0, 'end_paragraph_id': 11, 'end_character': 201, 'bleu_score': 0.943604326170661, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4190571618322229756}, 'section': 'Section::::Meaning.\n'}]}]