Origin of the similarity of "god" and "good"

Solution 1:

The prevalent idea is that God is not derived from good:

• Popular etymology has long derived God from good; but a comparison of the forms ... shows this to be an error. Moreover, the notion of goodness is not conspicuous in the heathen conception of deity, and in good itself the ethical sense is comparatively late. [Century Dictionary, 1902] (Etymonline)

The very interesting following extract from Antoly Liberman explains in detail the credible assumptions behind this assertion, and shows that it is "scientifically proved" despite many folk etymologies that tend to disagree:

• Good has transparent etymology: gather and -gether are related to it. Their root means “fit, suitable.” This circumstance is borne out by numerous cognates in and outside Germanic. That is “good” which has been “fixed,” “assembled,” “put together” in a proper way. By contrast, the origin of ‘god’ is debatable, which does not mean that we know nothing about its derivation.

.............

• After the conversion to Christianity, a word for “God” became necessary, and it had to belong to the masculine gender. This is indeed what happened: the singular was abstracted from the plural, and the neuter yielded to the masculine. Whatever the etymology of god may be, god and good are not related. I should also say that reference to intuition, if intuition means an undisciplined emotion, should be avoided. Etymology is a study of word history and presupposes a professional look at the development of sounds, grammatical forms, and meaning in many languages. “Intuitively,” deus and theos are two variants of the same word, but they are not. The term folk etymology covers suggestions of the theos-deus and god-good type: the temptation to connect look-alikes is irrepressible, but, unless we choose to remain in pre-scientific etymology, it should be resisted. Although “scientific etymology” stumbles at every step, there is no need to make it limp even more by burdening it with naïve medieval hypotheses. I sincerely hope that no schism will be the result of this post.