What is the purpose of だろう in expressions such as 何をしてんだろう or なんてかわいい犬なんだろう or 何でだろう

Question

The first one is the most confusing one, because I have heard people say it usually when they are upset. The other two examples to me sound a little softer with だろう/でしょう. Therefore, I suppose the purpose of だろう is to make the sentences, including the first one, sound a little less direct? The second example is also interesting, because of the んだろう part. Would it be a big difference, were the sentence written with only だろう, or even without だろう?

I read about the origin of だろう/でしょう, but it was not much of a help. I think I might be missing the nuances of these words now, but might develop a feel for them later on. They don't always translate well as "might" or "maybe" or "I wonder" etc.

Answer 1

だろう at the end of a sentence containing interrogatives ("wh-" words like 誰, 何, なんで, etc) means "I wonder". While an ordinary question is addressed to others, だろう(か) forms a question addressed to yourself. でしょう is the polite equivalent. Please remember the basic patterns below:

• 彼は来るだろう。
  I believe he will come.
• 彼は来る(の)だろうか。
  I wonder if he will come.
• 誰が来るのだろう。
  誰が来るのだろうか。
  I wonder who will come.
• 彼は来るのか。/彼は来るのですか。
  Will he come? (direct quesition)

So 何をしてんだろう (contraction of 何をしているのだろう) means "I wonder what they are doing". It could be translated into English as "What are they doing?", especially when the speaker is upset, but it's important to remember this is not an ordinary question that directly expects an answer from someone. Likewise, 何でだろう is "I wonder why". Unlike 何でなの (which directly asks "Why?"), a listener doesn't have to reply.

なんてかわいい犬なんだろう is "What a cute dog!". Although this だろう is still a "I wonder" marker here, this is a special exclamatory construction you have to master separately. This pattern always starts with なんて, なんと or なんという. See: JLPT N1 Grammar なんという / なんと / なんて

Related: だろう in question context?