I should hasten to point out that I am referring to Ficus carica and I would add that in my opinion, there is nothing common about a fig.
Dunno how that expression came about, for to me a fig is not something without value, but rather a wonderfully exciting part of the good life:
I am trying to figure out why everyone says you can't propagate a fig tree by rooting soft stem cuttings in water. I guess I'll find out the time honored way--by trying it to see what happens. So far there are zillions of adorable little white things that sure look like roots to me sprouting in delightful circles all around the stem at every node. They were already visible in just 3 or 4 days. Maybe I should go dig up some potting soil.
Here is one version of how that saying about a fig may have come into being: