Meaning of Sanatana

I have not seen a Pali word “santana.” Is it in a sutta? Where does it appear?

Yes. There are similar-sounding words common to Buddhism and Hinduism. 

“sanantana” appears in Verse 5 of Yamaka Vagga of the Dhammapada:

“Na hi verena verāni
sammantī’dha kudācanam
Averena ca sammanti
esa dhammo sanantano“

“sanantano” in the above verse differs from “santana,” which is not a Pali word.

“santanano” can be interpreted as “leading to the end of “san” (i.e., “san” + “anta” where “anta” means “end”). Here “sanantano” means  “end of ‘san’ is accomplished with“

Thus, the verse can be translated as follows:

“Hatred is never appeased by hatred 

It is appeased only by loving-kindness

Non-hatred leads to the end of “san” (“san” + anti” rhymes as “sammanti“)

That Dhamma (Buddha Dhamma with non-hatred or loving-kindness) accomplishes the end of ‘san’“

To attain the ability to generate genuine and automatic “non-hatred,” one must understand and follow the “anicca nature” of this world. Mere adherence to “non-violence” as a “sila” cannot achieve genuine and permanent “non-hatred.” In other words, only the “Ariyakānta sila” of a Sotapanna Anugami or above can have the basis of that mindset.

Thank you, Lal! Your response shed much light and made me think of a few things.

First, Aniduan wrote: “Upon Google search the word Sanatana Dharma comes up as eternal truth in Hinduism”

I thought that he had a typo and left out the “n”, and thus I thought of the above Dhammapada verse. This is because I have seen only this kind of translation for the verse;

It is not by hatred that hatred
subsides here anytime.
but by non-hatred they subside.
this is an eternal law.

The last line is always translated as:

this is the timeless Truth
this is the eternal law
etc.

I suppose this is another example of conventional meaning vs deeper meaning. I have not seen sanantano explained this way — as the end of “san” — although it makes a lot of sense, based on what we have been learning here.

Another question about the Pali breakdown: it seems like “anti” (in sammanti) and “anta” (in sanantano) are the same meaning components (the end) in different forms?

Related to the above, I was reading the latest post: Uncovering the Suffering-Free (Pabhassara) Mind

Under number 12, we have the phrase “sīti bhavissanti“, meaning “will be fully cooled down“. Does bhavissanti break down to “bhava” + “anti“?

1. The Wikipedia article “Sanātana Dharma” says: “Sanātana Dharma refers to the “eternal” truth and teachings of Hinduism.

2. Buddha Dhamma is also an eternal Dhamma: It describes the world’s true nature. In the above verse, one such truth is that “That Dhamma (Buddha Dhamma with non-hatred or loving-kindness) accomplishes the end of ‘san’“ as I explained above.

3. Many of the teachings in the Vedas are mundane versions of the Buddha Dhamma taught by Buddha Kassapa, who appeared before Buddha Gotama. Of course, all Buddhas teach the same Paticca Samuppada Dhamma.

• As I have mentioned previously, many “Buddhist concepts” existed (in watered-down, mundane form) when Buddha Gotama was born. His mother had taken the “eight precepts” on the day the Buddha (Bodhisatta) was born.

Lang asked: “Under number 12, we have the phrase “sīti bhavissanti“, meaning “will be fully cooled down“. Does bhavissanti break down to “bhava” + “anti“?”

• It is a bit different.
• A related word is “bhavissati” meaning “bhava” + “assa” usually referring to “staying in a certain way” or “to live accordingly.” 
•  “bhavissanti” is plural.
• Of course, “sīti” means “cooled-down state,” another synonym for Nibbana.