This time I got a question about a word that I wasn't really that familiar with. A reader asked about the etymology of the word sechus סחוס - "cartilage", and correctly pointed out that this is not a biblical word (and was curious what the biblical word was).
Klein, in his entry for sechus, writes:
This word arose through a misreading of חסחוס as הסחוס, whose ה was mistaken for the article and was consequently dropped. For a similar misreading see דות.
Before we get to chas'chus חסחוס, let's look at the misreading he mentions. In this case, the word chas'chus was read as has'chus, meaning "the sechus". The second example he gives, dut דות - "pit, cistern", was a misreading of the word chadut חדות as hadut הדות. A slightly different example that Klein doesn't mention, but might be more familiar to us, is the misreading of the word for sunrise, הנץ hanetz (a verb meaning he - the sun - shone) as "the netz", and therefore saying things like a "netz minyan" (with 690 hits on Google, compared to 20 for "hanetz minyan").
Now to chas'chus itself. Klein doesn't really give an etymology, but just says that it has related words in Aramaic, Syriac and Akkadian (hasisu), and that it should be compared to chasa חסה - the Hebrew word for lettuce, deriving from the Aramaic חסא - for which he says the etymology is unknown. He gives no clue as to why words for cartilage and lettuce would be connected, but Jastrow says that chas'chus might derive from the root חוס meaning "protection", and as I mentioned in the comments on this post, the leaves of the lettuce surround the core in a somewhat protective way. So maybe, but otherwise your guess is as good as mine.
This book points out that other Akkadian words for body parts have a similar feature of reduplication, and some of the examples he gives have Hebrew cognates. So the Akkadian word for skull, gulgullatu, is cognate to the Hebrew gulgolet גלגולת, and the Akkadian word for "head", qadqadu, matches the Hebrew kodkod קודקוד.
However, Klein's is not the only theory for etymology of chas'chus. Holma's Physiological Words in Assyrian-Babylonian writes that the Akkadian and Syrian words (kaskasu, kuskasa) for cartilage could derive from kasasu, "to gnaw," which would make it related to the Hebrew root כסס, also meaning "to grind, chew, gnaw." If so, it would be related to the word couscous as well, which has the following origin:
from French couscous (16c.), ultimately from Arabic kuskus, from kaskasa "to pound, he pounded."
Now to the writer's question as to the Biblical word for cartilage, I wasn't able to find one. However, the Aramaic translations to the Torah, and the Talmud identify chas'chus with the Biblical tenuch תנוך. That word, as part of the phrase תנוך אוזן - tenuch ozen - means "earlobe", and while the earlobe itself does not contain cartilage, other parts of the outer ear do. As discussed here, "the has'hus refers to all parts of the ear that are thicker than ordinary skin". So this is probably as close to a biblical word as we're going to get...