All right! It's time for some 'bad' words :-)
The other day I noticed an interesting pattern in the etymology of words denoting bad.
ചീത്ത sounds very related to ചീയുക - to decay
അഴുക്കു comes from അഴുകുക - to decay
കെട്ട comes from കേടാകുക - to go bad, e.g. milk
So, it seems, that originally bad meant not fit for consumption.