1
general::
1. In the customary or expected order, naturally, as in The new minister did not, of course, fire the church secretary. This usage, first recorded in 1548, employs course in the sense of "ordinary procedure." 2. Certainly, as in Of course I'll answer the phone, or Are you going to the meeting?? Of course. [Early 1800s] Also see MATTER OF COURSE.
American Heritage Idioms
2
general::
Phrase(s): of course
yes; certainly; for sure. • Sally: Are you ready to go? Bob: Of course. Sally: Then let’s go. • Jane: Are you coming with us? John: Of course. I wouldn’t miss this for the world. • "And you’ll be there, of course?" asked Alice. • "I would be happy to help, of course," confided Tom, a little insincerely.
McGrawhill's American Idioms And Phrasal Verbs