Here's a breakdown of the phrase:
* nanam: smell
* kettu: went away, disappeared
* eppoll: when
The phrase is used to ask when a particular smell disappeared. It can be used in various contexts, such as:
* Asking about a bad smell: "When did the smell of burnt food go away?"
* Asking about a pleasant smell: "When did the smell of fresh flowers go away?"
* Asking about a specific smell: "When did the smell of the perfume go away?"
It's important to note that the word "kettu" can also be used in other contexts, but in this specific phrase, it refers to the smell disappearing.