There's an article in today's Daily Mail about Mark Forsyth's book The Entymologicon, which looks at the connections between words. Here are a few from the book and article:
Castor is the Latin word for 'beaver' and castor oil was a substance originally extracted from the glands of a beaver. Bizarre is from the Basque word for beard, bizar. Apparently, Spanish soldiers arrived in remote Pyrenean villages, they appeared strange with their unusual beards. The word serendipity was coined by Horace Walpole, son of the first prime minister, in 1754 after coming across the name the island of Serendip, present-day Sri Lanka. Nazi is from the formerly common Bavarian peasant name Ignatius, and was coined as an insult.
Here's the article.