The expression “woe is me” (meaning) looks strange. On the surface, it seems to mean “an unhappy event is me”. Sure, it's an old idiom, undoubtedly reflecting vocabulary or grammar that is no longer productive in modern English. But what old language feature does it reflect? Is woe used as an adjective which is the complement of the verb and me an inverted subject (in which case, why isn't it “woe am I”)? Or does it mean “misery is me”, as in, “misery fills my soul so that I am misery personified”? I understand “woe betide me” (ok, not the most common object) and “woe [is] unto me”, but “woe is me” puzzles me.
Grammarphobia states that woe is the subject, but it isn't clear how the rest of the sentence is constructed. As a shortening or evolution of “woe is unto me”? How did that happen?