The simple answer for why lea references the concept of effective addresses in its name is that it is intended for calculating effective addresses. Names and intentions often go together (although I wish they did more often - there are endless examples of unnecessarily obscure terminology in this field).
Perhaps the problems people often have understanding the purpose of lea have more to do with the term 'load'. 'Load' suggests that a memory operation is performed, although it is not. This is even more likely to be confusing because there is a conceptual association between effective addresses and memory. Finally, the syntax of the memory operand to lea is that of a operand that in other instructions denotes an actual load. Given all this, some initial confusion over whether or not lea produces a memory access is understandable.
Perhaps a better mnemonic would have been cea, 'calculate effective address'. Oh well.
