To my mind a person or the society itself provides connotations to words based on experiences or beliefs.In other words, connotation refers to the feelings associated with the object described by the word, it is algo linked to the thought that comes immediately to the mind of a person when listening to a word.
An example could be the word stereotypes which gained a negative connotation and is more commonly associated with discrimination, when it actually refers to a natural mechanism used by people to better understand the world.
