Hi guys, here's something weird that I don't have an answer for. A few weeks back, Judy posted about the phrase “It is I,” which sounds awkward but is actually grammatical. This is because nouns following the verb “to be” appear in the predicate nominative, meaning that whenever you see a noun after is/are/was/were/being/been, it will take the nominative (subjective) case. This doesn't matter most of the time, since English speakers don't have to deal with the declensions of nouns--except where pronouns are concerned.
I like to think of the various forms of “to be” as the grammatical equivalent of an equal sign. What appears on one side of it must also appear on the other. If we were to say, “My friend is Mitch,” for example, “my friend” is the subject, and appears in the nominative (subjective) case. But “Mitch” follows a form of the verb “to be,” and so is also nominative, even though it's part of the predicate (hence the term predicate nominative). So we could say that “My friend = Mitch,” and since they're equivalent (both noun phrases are nominative case), the opposite is also true: “Mitch = my friend” or “Mitch is my friend.” This is why we can say something like “He is my friend,” even though we started with “My friend is Mitch.” They're exactly the same sentence. It's also the reason why odd-sounding things like “My friend is he” or “It is I” are grammatical, even though they sound awkward. Since the noun phrases are equivalent in terms of case, you can flip them. And when you do, "I am it" sounds perfectly fine, right?
So why does “Woe is me” exist? Shouldn't it be “Woe am I”? I don't think you'd ever catch anyone saying, "Me is woe."