Webster's dictionary online has a word-of-the-day that you can subscribe to. These are usually unusual or archaic terms that aren't in common usage.

For instance, today's word is uncanny, which has its roots in 18th century dialogue, meaning "weird" or "strange", but also has overtones of supernatural or superhuman powers, because of its usage in the popular comic book "The Uncanny X-men".

If you read further, they also describe the word "canny", which is, oddly, not an antonym (opposite) of "uncanny", but instead means "shrewd" or "clever", and has its origins in 16th century business terminology.