1610s, from above and board (n.1). "A figurative expression borrowed from gamesters, who, when they put their hands under the table, are changing their cards." [Johnson]
权威例句
1. I didn't have to bribe anyone; it was all open and aboveboard.
我没有必要贿赂任何人, 这完全是光明正大的.
2. His part in the affair was quite open and aboveboard.
他参与这件事完全是正大光明的.
3. He had been open and aboveboard, and there was nothing to fear.