in open sight; without tricks, concealment, or disguise: Their actions are open and aboveboard.
Origin: 1610–20;above + board; so called from the requirement of keeping the hands above the table or board in order to discourage possible cheating at cards
1610s, from above and board (1). "A figurative expression borrowed from gamesters, who, when they put their hands under the table, are changing their cards." [Johnson]