Heap-Organized Tables and 'Heap' the Data Structure
In computing generally a "heap" is just a general dumping ground, available for allocation then a block of memory/disk is needed. See https://en.wikipedia.org/wiki/Memory_management#HEAP for a lot more detail.

The data structure called a heap can be used to manage the allocation of space, or to operate as a priority queue, amongst other more minor uses. See https://en.wikipedia.org/wiki/Heap_(data_structure)

In a database, and more generally, a storage heap may be managed by a head-based data structure, though that does not have to be the case: the names being the same does not imply that they are in any way mutually inclusive.