When I learned Discrete Mathematics, I was curios why it is called "counting" the chapter that discusses permutation and combination. Isn't that mathematics about counting after all? But, I didn't think about it further until I need to revisit Discrete Mathematics again today.

Now I found the answer: it is because in that particular chapter you actually count something discrete with your finger like when you count the number of sheeps passing in front of you if you cannot sleep. The problems in that chapter are always in the form of "How many ...?" asking you to count something discrete like "How many pencils ...?" Well, naturally you will use your finger to count from 1 to N although the many techniques in that chapter (e.g., multiplication principle) will just make everything simpler by enabling you not to use your hand literaly to count something discrete.