The etymology of the words “consummate” and “consume” are completely different. The former is from con (altogether) and summa (sum total; taken from summa (highest supreme)): my interpretation is “union with god”. Which fits with its adjective definition: high degree of skill; complete or perfect. The later, to consume, is from con (altogether) but added to sumere (take up). And if someone were to altogether-take-up I would assume that there would be nothing left.
