***** NOT A TEACHER *****
(1) You have asked a very scholarly question. You will have to study some books or articles on the Web that explain the historical development of English.
(2) I am delighted to share the very little that I know.
(3) About 400 years ago, the English people started using "do" in questions and the
(4) For example, if you read Shakespeare, you will see examples of questions and the
negative that do NOT use "do."
(5) I am now reading one of his plays. Here are some sentences that I see:
I know not.
Why keep we her?
Know you the musicians?
(6) Then the English people started to use "do" for questions and the negative.
(7) This "do" is called an auxiliary, It is a helping verb. It does not mean anything.
(8) Can you change those three sentences in (5) to modern English? MAYBE the
I do not know.
Why do we keep her?
Do you know the musicians?
(9) Let's look at your two sentences:
When do we expect the rain? MAYBE 400 years ago, you could ask:
When expect we the rain?
What do I do now? MAYBE in past years, it was something like: What do I now?/ What now do I?
(10) Here is a sentence that confuses many learners: "She did it." Would you please
change it to the question? I'm sure that you answered: Did she do it?
If I have given you any accurate information, I wish to credit the one and only Professor George O. Curme in his two-volume masterpiece A Grammar of the English Language.
Student or Learner