Why is the malloc () pool called a heap?

Question

Can someone explain why the memory pool managed by malloc() / free() is called a heap?

Based on [1]: http://www.google.com/url?q=http://gee.cs.oswego.edu/dl/html/malloc.html&sa=D&sntz=1&usg=AFQjCNHaQLotbBKKwYqxiiYWN1146BWzFw, "Doug Lee explains how its malloc () "works, it is not obvious that the data structure, which we call the heap, is used at all.

We call this a “heap” because malloc() implementations usually use the best choice of memory fragment to return, and this has historically been implemented using a mini-heap of chunks sorted by block size?