While it might seem like a circular definition, it's important to understand that "sinister" has evolved in meaning over time.
* In Latin, "sinister" originally meant "left". This was because the Romans, like many ancient cultures, associated the left side with bad luck or evil.
* Over time, the word took on its current meaning of "evil" or "threatening".
Therefore, "sinister" is both the root word and the ultimate source of the English word.