Other effects may grant Keywords. 1. The definition and rules of the specific Keyword will determine the behavior if a Keyword is granted while it is already present. 2. The effect that granted the Keyword will specify the duration for which it is granted. 3. If an effect that grants a Keyword does not specify a duration, the duration is as long as that Game Object remains on the Board or in its current Non-Board Zone.
§ 801.3.a Core Rules PDF (officieel)
§ 801 A Keyword is a specific term that appears on Cards that acts as a shorthand for a specific game effect, or ability of any variety.
§ 801.3 Keywords can be referenced or specified by other Game Effects.