Course as defined in the scenario above means movement along a path. The word discourse could therefore be broken into two:
dis - which plays the role of a prefix and ;
course - the root word meaning movement along a path
The prefix usually means : to break, move apart, deviate or opposite of something. Therefore combining the root word and the prefix, we might define discourse to mean a discussion or talks which isn't just in a certain direction or path, it could be characterized as being unusually long covering various fields.
