This is not a new name... in the theory of algebraic data types there is a model of what it means to add and multiply types, resulting in "sum" and "product" types. I am not 100% sure but I believe these terms have been used since the early 70s.

The term "union" as used in C is highly related but not quite the same. If you add a tag to the union (and so have a "tagged union", often represented in C as a struct with an enum and a union) then you are equivalent in an information sense (but the usage is still different, as a C union says something very specific about how memory is used).