Erro

Today, I learned the word aberrant¹ which means “different from what is typical or usual”. This word has the prefix ab- (meaning “away”) and the substring err, so it was not hard to guess what it means (although if you considered the prefix ab- as negation of the second element (just like abnormal), it would not really make sense). The err part comes from the Latin verb errō, meaning “I wander, go astray”.

One obvious English descendant of this word errō is err (or error) meaning “to make a mistake”. The second most common word, I assume, is erratic, meaning “moving or behaving in a way that is not regular” (to be honest, I didn’t notice that this is related to err). Another adjective errant² also has a similar sense, “behaving wrongly”.