Sentence:  Two saints are credited with giving St. John's wort its name. One was St. John of Jerusalem, who used the <WSD>wort</WSD> (plant) during the crusades to heal his knights' battlefield wounds, and the other was John the Baptist. 
Meaning of the word marked with <WSD> tags:  Any of various plants or herbs, used in combination to refer to specific plants such as St. John's wort, or on its own as a generic term.