Have you ever noticed that people who lack compassion are called “ruthless,” but the most caring, empathetic person in the world isn’t called “ruthful” or “ruth”? That’s a relatively recent development; up until the 1800s, “ruth” was a relatively common word, and sure enough, it meant the opposite of “ruthless.”
“Ruth” entered English long ago, around the 1200s, and is a variation of “rue,” as in “I rue the day.” It was used as a noun: “It fill’d his heart with ruth For the poor helpless maid,” and also in phrases such as “have ruth:” “Have ruth on me, and let me go!” Another usage was to “take ruth,” as in “Mayhap the miller will take ruth on me.”
For some reason, though, “ruth” has been forgotten while “ruthless” is doing just fine. It’s much the same situation with “hapless.” A hapless person is unfortunate, inept, and generally in bad straits. Just like “ruthless,” it used to have an opposite: “hap.” By coincidence, “hap” entered English at about the same time as “ruth,” and disappeared in the 1800s, leaving behind only its opposite. “Hap” meant good fortune, and as the Earl of Surry pointed out in 1557 with “My hap is turned to unhappinesse,” it’s also the basis of the word “happy.”
Although they’re not as common as “ruthless” or “hapless,” there are at least a couple of other words that live on as negatives, having lost their positive versions. “Feckless,” for example, means someone or something that makes no difference to anything. It’s based on the obsolete word “feck,” which was a Scottish word derived from “effect.” In this case the original word isn’t quite as old as “ruth” or “hap,” and although you’ll never hear “feck” anywhere else, supposedly it’s still used — although rare — in some Scottish dialects.
Another negative that’s lost its positive is the rare “gormless.” This is a word that’s never been used much in the US, and its positive root “gorm” or “gome” died out before the US even existed. “Gormless” means lacking good sense, although “gorm” was not precisely the opposite — it meant paying attention. “Gorm” is extremely old; it came from Old Saxon, and by about the 1500s nobody was using it. Something weird happened in the 1700s, though, the negative term “gormless” appeared, centuries after “gorm” had apparently fallen out of use.
But maybe it hadn’t! The first appearance in print of “gormless” is from a 1746 book on dialects around Lancashire England. So maybe “gorm” was still alive in those parts too. “Gormless” seems to have gained a bit of popularity after Emily Bronte used it in Wuthering Heights. Same sort of thing happened with Air Jordans: some specific thing gets associated with a big star and pretty soon ruthless marketers have every hapless, feckless, gormless nobody wanting the same thing.