A great case in point: Using the word “will” for English’s future tense came from the other meaning you know of “will” (to want, as in “I will this to happen”).
On the one hand, certain natural human behaviors cause languages to grow in length and complexity. For example, the need to express things via metaphor and analogy causes unexpected combinations of words to form. A great case in point: Using the word “will” for English’s future tense came from the other meaning you know of “will” (to want, as in “I will this to happen”). That meaning morphed into a way to describe things the speaker would eventually do (i.e. “I will go” meant “I want to go”). Over time, that use became more generalized, resulting in the future tense we use today.