“Pearls of wisdom” means a wise statement metaphorically as precious as pearls.
Since very ancient times, pearls, though of small size, have been associated with high value, goods best appreciated by a perceptive audience. Therefore, aphorisms, adages, admonitions, and other nuggets of sage advice would be characterized as pearls. The term is also used sarcastically to denigrate any superficial, banal, or simply wrong-headed opinion that conflicts with our own.
The phrase is now considered a cliché, which makes its use in sarcasm apt.
Pearls of wisdom first appear in John Langland’s poem Piers Plowman in 1362 and we’ve since had versions such as do not throw pearls to swine. The reference is Biblical, to the Gospel of Matthew, which in the King James version is, “Give not that which is holy unto the dogs, neither cast ye your pearls before swine.”
Another example of the metaphor in print is this couplet, in which the reference is undoubtedly to pearl fisheries of various parts of the tropics: The Task, by William Cowper, 1781:
But wisdom is a pearl with most success
Sought in still water, and beneath clear skies.
You’re not likely to find a pearl by looking inside one of the oysters you slurp. Food oysters are able to produce pearls, but these tend to be small, irregular, and worth very little. Pearl oysters are in a whole different bivalve family, and create the pearls you wear around your neck.
Pearl oysters create pearls when a hard particle is coated with calcium carbonate (nacre) after entering the oyster. The oyster creates this nacre in order to cover irritants that enter its shell, often an invading worm or a bead placed there by a human pearl farmer.
One type of pearl oyster is the black-lipped pearl oyster, which can produce a black pearl. These oysters tend to be camouflaged in sand and algae, which is important since over-exploitation has caused populations to drop dramatically in the past.
Do you suppose there’s any difference between shiny white wisdom, and shiny black wisdom?