This is the 9687th most frequent Russian word.
чечню
"Чечню" is the accusative case of "Чечня" (Chechnya), referring to a region in Russia.
The word 'Чечня' is in its prepositional case form 'Чечне', used here to give the context of location.
В Чечне красивые горы и чистый воздух.
Chechnya has beautiful mountains and clean air.
The word 'Чечню' is in its accusative case form, used here as the object of the verb 'посетить' (to visit).
Я мечтаю посетить Чечню.
I dream of visiting Chechnya.
The word 'Чечня' is in its possessive form 'Чечни', indicating the relationship of 'история' (history) to the location it discusses.