1) op-ed I think most people know the word "op-ed ", but I don't think they know it stands for opposite editorial.
Sometimes a newspaper even invites opinions or short articles from local people.
2) columnist I used the "n" and I think I usually hear it that way, so colum'n'ist.
3) underdog underdog is sort of the and opposite of top dog, if you think top dog is someone at the top of the hierarchy and an underdog is a little guy somebody who seems to have the odds stacked against him. It's not exactly opposite because top dog you usually talking about clear hierachical organization. but in underdog although they are at the bottom, it's not a hierarchy, it's someone who's not expected to win, even though they try very hard. People often supporting underdog because of their their zeal and their focus on winning.
4) big cheese Big cheese sounds sort of funny, so I think probably although a boss might call himself a top dog. He probably wouldn't call
???. (分かりません) I think it only be used as the joke by the person who is the big cheese.
5) ashes I think people say ashes because ashes is what remains are ashes are the remains of something that's been burnt. Even if there is a larger pieces in it.
6) diamond-studded
piece of metal that push through fabric or leather and has a backing on it so that it does not come out again. So a diamond -studded collar would be collar with diamond stuck into it on little pieces of metal. You can also say a tie stud. A tie stud is has a little pin that you push through the tie and shirt and you put a little back on it to keep it pinned to your shirts it doesn't flap around. A tie clip is the tack you slide on from the side. So almost anything that has the kind of a metal tease that stuck through fabric or leather can be called a stud. Then if you think of a week as a strip of seven days and few of them have a holiday, stuck into them. It's ・・・ I think you can imagine that it's a sort of similar idea to a diamond-studded collar.
7) sell like hotcakes When I was growing up, we usually called them pancakes, although I knew the word hotcakes. Another word for pancakes is flap-jacks.