Orphans don't have parents, but in bitcoin,
There is some terminology confusion between the Bitcoin community on Bitcointalk and the Bitcoin Core implementation.
In the satoshi codebase there is something called an "orphan block" which is quite literally a block which doesn't have a parent— the previous block is not known the the node yet.
The reason that a block which isn't in the longest chain— I'd call it a stale, abandoned, or extinct block— is called "orphan" by the community is because the generated transaction of a stale block displays "orphaned" in the transaction list. But here it's pedantically correct: The generated transaction has no parent in the blockchain, because the block that created it is not in the blockchain. The transaction list is the only way many miners bothered looking at blocks (instead of things like the debug.log or the source code, which call parent-less blocks orphans), and so they naturally started calling the stale blocks orphans.
Changing an enshrined practice is usually a lost cause, but the word orphan still causes confusion: it's still applied to blocks without a parent, and its the most intuitive term in that case. So I recommend using one of stale, abandoned, or extinct when referring to blocks that didn't make it into the longest chain though I don't begrudge people using the word orphan here too other than by noting the potential for confusion.
