Question: where did the superstition saying knock on wood come from
[{'answer': 'German folklore', 'provenance': [{'wikipedia_id': '1094458', 'title': 'Knocking on wood', 'start_paragraph_id': 3, 'start_character': 35, 'end_paragraph_id': 3, 'end_character': 50, 'bleu_score': 1.0, 'section': 'Section::::Origin.\n'}]}, {'provenance': [{'wikipedia_id': '1094458', 'title': 'Knocking on wood', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 144, 'bleu_score': 0.8196189957582151, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11987171507216483957}, 'section': 'Section::::Origin.\n'}]}]