a Greek toponym, derived from the tribal name Magnetes
Magnesia (regional unit), the southeastern area of Thessaly in central Greece
Magnesia ad Sipylum, a city of Lydia, now Manisa in Turkey
Magnesia on the Maeander, an ancient Greek city in Anatolia
Magnesia Prefecture, a former prefecture of Greece
Magnesia, a mythical city-state in Plato's Laws
The element magnesium is named after magnesia, not the other way around.
The origin of the name manganese is complex. In ancient times, two black minerals from Magnesia in what is now modern Greece, were both called magnes from their place of origin, but were thought to differ in gender. The male magnes attracted iron, and was the iron ore we now know as lodestone or magnetite, and which probably gave us the term magnet. The female magnes ore did not attract iron, but was used to decolorize glass. This feminine magnes was later called magnesia, known now in modern times as pyrolusite or manganese dioxide. Neither this mineral nor manganese itself is magnetic. In the 16th century, manganese dioxide was called manganesum (note the two n's instead of one) by glassmakers, possibly as a corruption and concatenation of two words, since alchemists and glassmakers eventually had to differentiate a magnesia negra (the black ore) from magnesia alba (a white ore, also from Magnesia, also useful in glassmaking). Michele Mercati called magnesia negra manganesa, and finally the metal isolated from it became known as manganese (German: Mangan). The name magnesia eventually was then used to refer only to the white magnesia alba (magnesium oxide), which provided the name magnesium for that free element, when it was eventually isolated, much later.[10]
http://en.wikipedia.org/wiki/Manganese#History
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