Dungeons and Dragons
It is often a source of much confusion for young or new students to history as it applies non-historical or outdated terms to weapons and armour of the medieval period as well as providing out-right wrong information, e.g. the current version shows a picture of a curved bladed sword and labels it a rapier.
Some "DNDisms" that may be commonly heard are:
Any reference to a 'plus (numeral) sword' is a reference to this game.