The first attestation we have of the word noble being used in the English language is from the Ancrene Riwle, which was an early thirteenth-century guide for nuns. It was probably borrowed directly from the Old French word noble, which had basically the same meaning as today and was in turn from Latin nobilis, which meant "famous" or "renowned". Earlier on, that was spelled gnobilis, and more literally meant "knowable". The root there is the verb gnoscere, which meant "to know". That traces to Proto-Italic gnosko, which ultimately comes from the Proto-Indo-European reconstruction gneh, still "to know". Usage of the word noble peaked in the year 1617 and has steadily been trending downwards since, except for large spikes in Decembers for some reason.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.