This is the 5724th most frequent French word.
chassieu
"Chassieu" is not a French word; it is a proper noun referring to a town in France.
Here, 'Chassieu' is used as a proper noun to refer to a specific place—a village in France.
Le village de Chassieu est charmant.
The village of Chassieu is charming.
Once more, 'Chassieu' is a proper noun referring to a location, and the phrase contextualizes the duration of residence.
Nous habitons à Chassieu depuis cinq ans.
We have been living in Chassieu for five years.
In this sentence, 'Chassieu' is similarly used as a proper noun indicating the place of residence of certain individuals.