Abarim Publications' online Biblical Hebrew Dictionary
None of the consulted sources reports an etymological connection between the two verbs טוב (tob) and יטב (yatab), but even if technically there is none, to any member of a Hebrew audience, the two are very obviously closely akin. Then, the existence of the names Tebeth and Tabbath suggest that there was even an otherwise unused root טבב (tabab), which probably meant something like to be perpetual, to be stable, to keep forever.
The word tob covers that ethical extreme "good" about which so many people have thought. Because what is it? What is goodness and what is virtue? The only answer possible, or so it seems, is to define goodness as that which brings about the inevitable, as set by God. The opposite ra, may then be defined as that which thwarts it. Ultimately, good is that toward which the universe develops; the attractor of all evolution — because, no, evolution does not happen by dumb chance but by settling into stable conditions. Evil, on the other hand, describes instability or the falling apart of unstable elements due to stronger formative forces. Evil's ultimate fate, of course, is to be overcome.
It's a misconception to maintain that at the fall, mankind was rendered discernment between good and evil. Prior to Adam and Eve's consumption of the fruit, there was no knowledge of evil. As they ate, they gained knowledge of good and evil. The problem is that the difference is unclear. As long as we have no reasonable idea where God is taking us, or how he's doing it, we have no authority to judge over good or evil. All we can do is follow Law.
Like our English word "good," the Hebrew verb טוב (tob) is also used to indicate being pleasant (Numbers 24:5), pleasing (2 Samuel 3:19), joyful (Judges 16:25, Ecclesiastes 7:14), of quality (Judges 11:25), and positively inclined (Numbers 11:8).
This verb's derivatives are:
- The identical adjective and noun טוב (tob), both meaning good (Genesis 1:4, "and God saw that it was good"; Genesis 6:2, 1 Samuel 25:8).
- The masculine noun טוב (tub), meaning a good thing (Genesis 45:18) or goodness (Psalm 119:68).
- The feminine noun טובה (toba), meaning good or welfare (Deuteronomy 23:7, Ecclesiastes 5:10).
The verb יטב (yatab) means to be or do good (Exodus 1:20), well (Genesis 12:13), glad (Judges 18:20) pleasing (Genesis 34:18), justify or make-good (Proverbs 17:22), or do well (Genesis 4:7). It's used pretty much as an alternative to the verb טוב (tob). Our verb is also part of the familiar formula, "that it may go well with you" (Deuteronomy 4:40, 5:16 and eight more places).
The derived masculine noun מיטב (metab) means the best (Exodus 22:4, 1 Samuel 15:9).