I believe Anonymoose has the right of this. I don't speak Japanese, but it's quite likely that the Japanese name for the ability is an adverb plus verb phrase. Meanwhile, the English localization uses a word that is already a verb with certain connotations. In our case, plunge can mean diving into something (I plunge headlong into battle), and it can also mean stabbing something (I plunge my sword into his torso). The English translation saves on space by using a single word whose dual meaning is appropriate in context where the Japanese language doesn't have a word with that precise dual meaning.