means Capable of being wounded, attacked, or emotionally hurt — exposed and open to harm.

from From Latin vulnerare, "to wound," itself from vulnus, "a wound." The word arrived in English in the early 1600s carrying that literal sense of a body that can be pierced. The Latin vulnus may be distantly related to a root meaning "to tear" or "to pluck," though the deeper connections are uncertain. So at its core the word is simply the description of soft flesh and the blade that could find it — long before it ever softened into talk of open hearts.