While it's not exclusively a dictionary, Tolkāppiyam contains extensive sections on semantics and word formation, making it a valuable resource for understanding the vocabulary and usage of the language during its formative period.
However, it's important to note that:
* There might have been earlier Nigandu's that haven't survived. Tamil literature has a rich history, and older texts might have existed but were lost to time.
* Tolkāppiyam is primarily a grammatical text. While it offers insights into vocabulary, it's not a dictionary in the modern sense.
Therefore, while Tolkāppiyam holds the title of the first surviving Nigandu, the true first Nigandu might be lost to history.