Fighter clothing is modern generic term for clothing specifically designed with combat in mind.
Fighter Clothing in the SCA
Heavy armour includes the gambeson. This item is a padded coat that is designed to be worn under armour to protect the body from the effects of blows. A arming cap is a padded coif worn under the helmet.
Fighter Clothing in Reenactment
Reenactors also wear gambesons/aketons under their mail and arming doublets under plate harness. Where appropriate they wear padded coifs under helmets, unless the helmet has a proper suspension harness.