Not just my own, but surely every thinking person's favorite word-forming element is "--some," perhaps because It appears in so many cheerful formulations. If you experience a sudden, overpowering urge to transform a noun to an adjective then "--some's" the way to go.
Imagine yourself, for instance, writing a novel and searching for the words to describe your ingénue heroine. She's not just "handsome" and "wholesome" but also "blithesome," "lissome," "winsome" "toothsome," "cuddlesome" and perhaps even "frolicsome." Could you find a better word? Well, maybe. Perhaps "buxom?"
Most of these words are of obvious origin but a few are on the obscure side. "Winsome," one of the language's most delightful (or delightsome) adjectives, derives from the now defunct "wynn," meaning "joy". It's a word that apparently hid out in illiterate northern English dialect for a couple of centuries before it was resuscitated, to everyone's advantage, by Burns and Scott. "Lissome," which now means supple or graceful, comes from the old English "lithe" meaning mild, gentle, or meek. "Buxom" is drawn from a stem meaning "bow" and for most of the existence of the English language signified "compliant" or "obliging." "Buxom" began to connote zaftigity only during the middle of the last century. Here's the very best use of "buxom" in its long history. It's by John Milton -- the young Milton, not yet the epic Milton.
The frolic wind that breathes the spring,
Zephyr, with Aurora playing,
As he met her once a-Maying,
There on beds of violets blue,
And fresh-blown roses wash'd in dew,
Fill'd her with thee, a daughter fair,
So buxom, blithe, and debonair.
Candor compels us to admit that not all "-some" words are quite so bonny. There's also a "--some" underside: "irksome," "loathsome," "gruesome," "meddlesome," "fearsome," "noisome" (which now means" foul-smelling and is related to "annoy"), bothersome. Good mouth-filling words to describe the villain of the piece.
And then there's "fulsome" which for the longest time meant what it seems to mean, then latterly acquired the learned connotation "odious," which it is now in the process of shedding. And "awesome" which has deteriorated from "filled with awe" to meaning "cool" -- and has become a favorite adjective of praise to an entire cohort or generation of the vocabularially deprived.
No one can say, "unbuxom" or "unblithesome." Yet we regularly say "unwholesome."
For the record, the "--some" in "threesome" is an entire different "--some," as is the "--some" in "chromosome."