Whom!

It's a bummer that when I learn a rule, I can't let it go.  One example is the usage of whom.  For a long time, I had no idea when I was s'posed to use it, and when who would be more appropriate. Then I learned about noun declension in German and Latin, and badabing!; since then I've corrected every who/whom mistake I have seen; sometimes in my head, sometimes out of it, always with a pang of embarrassment that I can't let go.

By the way, if you ever have a question as to which you should use, just ask yourself: "Is who/whom referring to the subject of the sentence?" If so, use who; otherwise, use whom.

I don't know where whom /hūm/ came from. I know that in German, the Dative form of wer (which means "who") is wem (which means "to whom"). Wikipedia will tell you more, I'm sure.