The verb enervate means to weaken or destroy the strength or energy of. Its near homophone innervate—which is usually used in biological contexts with regard to nerves, though it's sometimes used figuratively—means to stimulate to action. Because enervate sounds somewhat similar to both energize and innervate, it is sometimes treated as if it were synonymous with those words.
Just to note, these words are actual, and not simply near, homophones in dialects with pin/pen merger, which can lead to further confusion.