The Online Etymology Dictionary is the work of a Pennsylvania-based historian and linguaphile, Douglas Harper, who writes on the home page, “This is a map of the wheel-ruts of modern English. Etymologies are not definitions; they’re explanations of what our words meant and how they sounded 600 or 2,000 years ago.”

Although the dictionary is about English, you can sometimes see foreign-language relationships if you type in foreign words. For example, enter gestern (“yesterday” in German) and you will get an entry mentioning it in connection with the word “yesterday.”