The usual etymology of νότος derives it from ὀνοτός, verbal adjective of ὄνομαι (see νότος / ὄνομαι). Now νόθος "bastard" was also derived from the same verbal adjective ὀνοτός (see νόθος / ὄνομαι). Therefore, both νότος and νόθος having the same etymon, their relationship led to the idea that the one could be the etymon of the other, in a new chain ὀνοτός → νόθος → νότος (illogical since νότος has the same /t/ as ὀνοτός, whereas νόθος has a /th/, which requires a change of /t/ to /th/ and then back to /t/).