We gain some, we lose some words

I often point out that as a living language, English grows and changes. But English not only adds new vocabulary, it also regularly loses words. That is, people sometimes stop using certain words. When that happens, dictionaries label the “lost” words obsolete or archaic.
While reading Lawrence Sanders’s, The Second Deadly Sin, I encountered just such a word.
Sanders wrote: “A cop was not paid to be compassionate. They were paid to see the shades of grey, to understand and dole out ruth.”
A few paragraphs later, he used ruth again: “All these other people — the ruth-givers — they modified the standard.”
Since I don’t use ruth and never hear anyone else do so, I looked it up. The OED tells us ruth is now archaic and suggests it is usually now employed only poetically.
Ruth has several meanings, the first being, “The quality of being compassionate; pity; compassion.” This seems to be what Sanders is saying in the second quotation. When he writes, “ruth-givers,” he probably means, “Those who show compassion.”
But in the first passage quoted, he tells us cops aren’t supposed to be compassionate, then inexplicably proceeds to say they “dole out ruth.”
He may be using ruth in its second sense here — contrition, repentance, remorse. Who can say?
Perhaps Sanders was counting on the fact that few people ever look up unknown words and consequently felt he could use ruth in a confusing way.
Ruth also means “sorrow; grief; distress; lamentation.” These different meanings all go back to Middle English when ruth was spelled reuve. It’s thought this word originated either in the Old Dutch (rouwen) or Old High German (riuwan), where the meaning in both cases was, “to cause regret.”
This ancient meaning is seen in the modern word rue, which has the same origin and which is a verb form of ruth.
I called rue modern because it’s still in common use. However, rue was recorded as early as 1440 when it meant, “To make one wish one had acted otherwise.”
Rue’s meaning hasn’t changed over the centuries.
Rueful, also from Middle English, is an adjective used to describe behaviour  which is sorrowful or that shows regret. The archaic word ruthful, means, “full of compassion.”
Ruthless, the opposite, or antonym, of ruth is still very much alive in Modern English. We hear and use it all the time. It means, “merciless.”
Ruth is also a proper name. Brewer’s Dictionary of Names says Ruth is from the Old Testament’s Book of Ruth. Brewer gives the origin as the Hebrew word for “friends” — ré-ut.
Seventeenth-century Puritans mistakenly associated the name Ruth with the English word ruth. So when a Puritan girl was named Ruth, her name was thought to mean “pity” or “sorrow,” rather than its true meaning of “friend.”
Modern name-your-baby books acknowledge the original meaning of the biblical name. 6,000 Names for Your Baby offers: “ RUTH (Hebrew) a beautiful friend.”
The word ruth, like kempt and sheveled, lives on mostly in the negative — ruthless, unkempt, disheveled.