The word 'satrap' is originally Persian, in its original rendition it's been reconstructed to mean (in Old Persian) something like 'Protector of the Province'. As I recall, whilst the realities of the position remained the same the actual Seleucid/Hellenistic term for these sorts of officials was strategos, but the majority of scholars continue to refer to them as satraps well into the Seleucid era because much of how they behaved and interacted with royal administration was unchanged.
The term 'satrap' is a transliteration, but it has also become something like a technical term in the terms used to describe elements of Empires. It's like the fact that 'Sheikh' is actually used as a technical term for certain figures well before the societies that actually used the term, particularly in Assyriology.
Ahh, thank for those details, never got a clear picture in the head.