Origin: Latin suffix -ous
Decorous has 3 different meanings across 1 category:
characterized by propriety and dignity and good taste in manners and conduct
"the tete-a-tete was decorous in the extreme"
according with custom or propriety
"her becoming modesty"
"comely behavior"
"it is not comme il faut for a gentleman to be constantly asking for money"
"seemly behavior"
Marked by proper behavior.
The word "decorous" comes from Latin, where it originally meant becoming, fitting, or proper. It is formed by adding an English suffix to a Latin root that relates to elegance and grace.