Esposa and spouse both come from the same root, and both mean the same thing — that one was obvious!
However, it gets more interesting: both come from the Latin spondere, meaning, “to bind”.
From this root we also get the Spanish word esposas, which means (in addition to meaning just “wives”), also means… handcuffs.
Yes, in Spanish, “handcuff” and “wife” are the same word. It gets the point across clearly, doesn’t it?