This is the 8503rd most frequent Russian word.
нин
The word "нин" does not have meaning in Russian; it may be a typo or misheard word.
Here, 'Нин' is used as a proper noun, presumably the name of a person, thus indicating the subject of the sentence.
Нин начинал свой день с чашечки кофе.
Nin started his day with a cup of coffee.
In this example, 'нин' is referred to as a word (in quotes) being identified from the context, illustrating a generic usage or mention.
Каждый узнавал слово 'нин' по контексту.
Everyone recognized the word 'nin' from the context.
In this case, 'Нин' is again treated as a proper noun, used as someone's pseudonym or alias, for identification or stylistic purposes.