The Sapir-Whorf Hypothesis is about the connection between language and thought.
The Sapir-Whorf hypothesis takes two forms: that language determines thought or that language influences thought. The former is a much stronger view because it states that one is incapable of understanding a concept for which the language has no name (it also implies that there is no thought without language). There is no empirical evidence supporting the strong version and considerable evidence that thought can proceed without benefit of language. However, the weak version plausibly suggests that different languages can “carve up” the world into different ways — or, put another way, that conceptual thinking can be shaped and constrained by available linguistic categories. As Whorf put it, “We cut nature up, organize it into concepts, ascribe significance as we do, largely because we are parties to an agreement to organize it in this way – an agreement that holds throughout our speech community and is codified in the patterns of our language”.
This is why controlling language is one of the first things tyrants and those who would control and manipulate other do. Co-opt and corrupt the language, and you can control the thoughts of the people more easily.