The word comes from Noah of Noah's Ark in the Bible.

The original language is Hebrew (before all the translations). In Hebrew, Noah's name is Noach. Hence, Noachide or Noahide. Both are correct.

In the Bible, Noah is called "righteous" because of how he lived, according to 7 Divine instructions (aka laws). These instructions were simple, not elaborate, as those later given only to the people (nation) of Israel.

So, really, a Noahide is anyone who was not born Jewish (or converted to Judaism). And just as there are observant Jews and non-observant Jews, there are observant and non-observant Noahides.

Kim