Active King
A king that participates directly in the fight, rather than staying passive, typically in the endgame once mating dangers have receded.
An active king can support pawn advances, attack the opponent's pawns, or approach the center, and its activity is one of the most important factors in evaluating who is better in a king-and-pawn endgame.
Etymology
Active is an ordinary English adjective of Latin ancestry rather than a coined chess word: it appears in English in the mid-14th century as actif or active, from Old French actif (12th century) and directly from Latin activus, from actus meaning a doing. In chess it is applied to a king that leaves safety and takes part in the play, a usage tied to the endgame phase. Wikipedia's chess endgame article states the principle directly: the king, which normally is kept safe during the game, becomes active in the endgame. No coiner, first user or dated first occurrence of the fixed phrase active king could be confirmed from any source fetched here, and Wikipedia's Glossary of chess has no headword for it.
First documented: n.a. — n.a. - no dated first use of the phrase active king found in fetched sources
Translations
Translations for this term haven't been added yet.