words that changed meaning over time

Gay.

Nice.
The source or origin of the word is the Latin word 'nescius' which means : ignorant or stupid.

From its Latin roots, nescius became the word 'nice' to the gauls of France, (pronounced 'neess' in French). Originally it had the same meaning as nescius : ignorant or stupid.

After The Battle of Hastings in 1066 A.D., Britain obtained a new ruler from France...William the Conqueror. More than 2,000 new words were added to the English language from
the French. Before this, the language spoken by the inhabitants of Britain was a very
rudimentary, gutteral language that barely had a few hundred words.

This is when the meaning of the word 'nice' began it's slow transformation from 'ignorant/stupid' to 'foolish' to 'shy' to 'fastidious' to 'refined' and finally to what we now have as today's modern definition of 'pleasant' or 'agreeable', which was first recorded in the 18th century.


Geek - variant of English dialect geck "fool".

Originally, it was a carnival performer whose act consists of outrageous feats such as biting the heads off live animals. Later, it was used for somebody regarded as unattractive and socially awkward. At present, it is used for somebody who is a proud or enthusiastic user of computers or other technology, sometimes to an excessive degree.          


Awful
Originally meant "inspiring wonder (or fear)". Used originally as a shortening for "full of awe", in contemporary usage the word usually has negative meaning.

Egregious
Originally described something that was remarkably good. The word is from the Latin egregius "illustrious, select", literally, "standing out from the flock", which is from ex—"out of" + greg—(grex) "flock". Now it means something that is remarkably bad or flagrant.

Artificial

This originally meant ‘full of artistic or technical skill’. Now its meaning has a very different slant.

Manufacture

From the Latin meaning ‘to make by hand’ this originally signified things that were created by craftsmen. Now the opposite, made by machines, is its meaning.

Counterfeit

This once meant a perfect copy. Now it means anything but.

Silly meant blessed or happy in the 11th century and went through pious, innocent, harmless, pitiable and feeble minded before ending up as foolish or stupid.

Pretty started as crafty this changed to clever or skillfully made, then to fine and ended up as beautiful.

Brave : Cowardice (as in bravado)

Girl: Young person of either sex

http://www.dailykos.com/story/2009/05/31/735843/-The-Mad-Logophile-Words-That-Have-Changed-Their-Meaning-Part-1