The word "significand", which I thought might have been invented
during the IEEE 754 standardization process, is instead cited in that
book as having been used by Forsythe and Moler in _Computer Solution
of Linear Algebraic Systems_ from 1967.
John Savard
A web search, though, shows that "What Every Computer Scientist Should
Know about Floating-Point" mentions this also, though I didn't notice
it at the time.
John Savard