Explain why the distributive property is sometimes called the distributive property of multiplication over addition.

To explain:

When using distributive property there are two ways to go about it you can use it in an addition problem, (which would be the more original or classic way) or  you could use it to solve a multiplication problem. So to expand, the distributive property was original made as a rule for addition but then it became a way to solve other thing which in your case is multiplication.

Sorry if you are confuse I am better at telling than typing. Hope this answered your question!