When I watercolor and apply paint to paper I "miss" a lot of spots. These "missed" spots where the white of the watercolor paper show through are called "holidays". When seamen, during the days of sail, missed taring parts of the sailing lines, the captain would send them back up even on the Sabath to coat those missed areas, hence the name "holiday". Ever heard; "I haven't got a clue?" It is really; "I haven't got a clew".