* A misspelling: There might be a typo in the phrase. If you can provide the correct spelling, it might be easier to understand the meaning.
* A regional or dialectal term: The phrase might be a local expression specific to a particular region or dialect.
* A made-up phrase: It could be a fictional term created for a story or other creative work.
Without more context, it's impossible to determine the meaning of "thanum an dhul." Please provide additional information, such as the language you are referring to, the context in which you encountered the phrase, or any other details that might help decipher the meaning.