above-board

The story

From above + board (“table”). First attested in 1610. Said by Johnson to have been borrowed from gamblers, who, when they change their cards, put their hands under the table.

First known use, by meaning

• First attested in the late 16ᵗʰ century. In open sight; without trick, concealment, or deception.
• First attested in the late 16ᵗʰ century. Honestly; openly.