The final post from the Koine Greek blog on the Greek word σκύβαλον is up and this one covers the metaphorical uses of the word. One such usage can be found in the book of Sirach.
When a sieve is shaken, the refuse appears;
so do a person’s faults when he speaks.
(Sirach 27:4, NRSV)
You might look at that translation and think that the word “refuse” is the translation of σκύβαλον but it isn’t. Rather, it is “faults” that renders the Greek word! On this Aubrey writes,
This proverb from Ben Sira presents a comparison that evokes the same agricultural context discussed previously (Σκύβαλον in agricultural contexts). In the sifting of the grain, the chaff flies away and the grain falls through. Only what’s large enough to not fit through the sieve remains: the refuse, dirt and droppings of the threshing oxen. The ellipsis in the second half forces readers to workout the comparison alone. The result is that Ben Sira does not have a particularly high opinion of man’s deliberative/rational prowess.
But this doesn’t necessarily mean that this is meant to be taken in a vulgar way like our word “shit” is today.
There are a number of other examples Aubrey offers so I suggest you read the rest of the post here and lament that this series is over!