safsal and asla

One of the fun things when doing etymological research is discovering two related words, that you previously had no idea were connected, but once you look into it the connection makes a lot of sense.

That's the case with the words סַפְסָל safsal and אַסְלָה asla. 

Here's Klein's entry for safsal:

PBH bench, stool. [From L. sub-selliam (= bench, seat), through the medium of Gk. suphellion, formed from sub (= under; see סוּבּ◌), and sella, from the base of sedēre (= to sit)]

Having safsal derive from the Latin subsellium makes even more sense when you note that some manuscripts of the mishna vocalize the word as safsel. 

The Latin sella - "seat, chair" - also appears in asla (today "toilet" / "toilet bowl"). Again, here's Klein:

PBH (pl. אֲסָלוֹת, resp. אֲסֶלּוֹת) closet stool, lavatory seat. [L. sella (= seat, chair, stool), for sed-lā, from sedēre (= to sit). ... The אַ◌ in אַסְלָה is prosthetic.]

The same roots for these Hebrew words have also made their way into English. The verb sedere made its way into such words as sedentary, preside, and sedate. And if we go back to its Proto-Indo-European root, *sed, we get even more English words, including very common ones like sit, set, and chair. 

That same PIE root, via Greek, gave us one more very familiar Hebrew word - sanhedrin סנהדרין. Klein provides the background:

PBH 1 ‘Sanhedrin’ — the supreme Jewish court (סַנְהֶדְרִין גְּדוֹלָה) in the time of the Second Temple, consisting of 71 scholars. 2 one of the lesser courts with 23 members, called סַנְהֶדְרִין קְטַנָּה, lit.: ‘the small Sanhedrin’. [Gk. synedrion (= council, council chamber), lit.: ‘sitting together’, from syn (= with, together with), and edra (= a seat), which is cogn. with L. sedēre (= to sit).]

The Online Etymology Dictionary gives a similar etymology, but has the Greek hedra for "seat." 

All these words represent very different kinds of "seats", each with their own purpose. Since sitting is such a common experience, it shouldn't be surprising that it has led to so many words - expressing both the literal and symbolic expression of the action.