Egg Someone On
This is one of those idioms where you think the etymology would be obvious, but it actually ends up surprising you.
You might be shocked to hear that this phrase has nothing to do with eggs. You may have thought that this expression means that people are being spurred on to do something for fear of being pelted with an egg. However, the egg in this expression is a verb meaning “to goad” or “to incite” which is derived from the Old Norse (Old Germanic dialect) word, eggia.
The word is related to the Old English word, ecg, meaning “an edge.” It is also related to the Middle Low German eggen, meaning “to harrow.” Therefore, this may suggest that someone is “egged” on in fear of being prodded with something sharp, but this is only a vaguely implied connection.
The word came into English around the year 1200, originally in the sense of provoking or tempting a person. Today, the phrase means to encourage someone to do something, usually of a risky, foolish, or dangerous nature. In other words, people egg one another on to get a reaction. For example, one may say, “don’t listen to him, he’s only trying to egg you on!”