'aboveboard' originates from the phrase 'above board,' where 'board' referred to a table. The term was used in card games to indicate that hands were kept above the table to prevent cheating.

'above board' was used in the 16th century to describe honest card playing, and eventually became the modern English word 'aboveboard' to describe honesty in general.

Initially, it meant 'keeping hands above the table to avoid cheating,' but over time it evolved into its current meaning of 'honest and open.'