ExS - I don't think that the 1800s were, officially, the middle ages.
"Universal" was a modification of GMT to whip the astronomers into line. Astronomers originally invented GMT, but defined zero as midday - which didn't tally with what the rest of the human race thought, so UTC is GMT with the day starting at middnight.
I *think* that astronomers still use GMT in the same way they always did, but the rest of the world are rebelliously determined to start our days at midnight. So, technically we may be using "GMT" incorrectly - but don't care!
G