I love it. "Often, the explanation of the so-called 'origin' of this phrase is accompanied with plausible-sounding historical or biographical details, giving it an unmistakable (but alas, totally spurious) 'ring of truth.'"

Then they proceed to weave a tale accompanied with plausible-sounding historical or biographical details, giving it an unmistakable (but alas, totally spurious) "ring of truth."

For another opinion, and one to which I would attribute more plausibility, see:

http://www.wordorigins.org/wordorb.htm#Big