The roots of both please and placebo are the same and the American Heritage Dictionary takes them back to an Indo-European root plak that meant "to be flat."
单词please和placebo有同一个词根，《美国传统英语词典(american Heritage Dictionary)》为它们追根溯源到了一个印欧语系的词根plak，意指“处于平的状态”。
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