It appears that the Ethereum developers decided to create special names for currency units rather than using an already established international standard (SI units
Why did the developers decide to go with:
- wei instead of atto-ether (aEther)
- szabo instead of micro-ether (μEther)
- finney instead of milli-ether (mEther)
Not only are SI prefixes well understood by most of the world's educated population (except the United States), they also naturally provide for many of the units in-between.
We are already seeing problems with the made-up denominations. We see things labeled as gigawei or GWei (which is really nanoether or nEther) causing further confusion.