It's not a big leap to think that hyena-like qualities should therefore inform gnolls' characteristics. It's been done to varying degrees before, starting back in Roger Moore's article in Dragon #63. I've never seen anyone work through all the implications of this, though. Certainly, it doesn't seem that's anyone's ever given much consideration to the folklore and historic beliefs regarding hyenas.
There are four species of hyena, but gnoll art tends to most commonly make them resemble the spotted hyena. Maybe there are more than one gnoll species, too? Perhaps there's a rare, gentle and insectivorous humanoid aardwolf. Or maybe they're not so gentle and they dine on formians?
Anyway, spotted hyenas are hunters and scavengers. They have powerful jaws and specialized dentition to crush bone--they are reported to outclass brown bears in this regard. They bring down game in packs, but they also follow other predators and steal their kills. They've also been known to dig up recently buried bodies from graves. Hyenas possess the ability to digest all the organic material in a carcass, including bone.
Male spotted hyenas are slightly larger than females, but otherwise there's very little to distinguish the sexes. Interestingly, even the external genitalia is similar due to the female's clitoromegaly (How's that for a conversational factoid?). Hyena clans, in fact, are matriarchal--led by an alpha female with high levels of androgens (male sex hormones).
Hyenas compete from birth. Particularly in same sex litters, neonatal fratricide (siblicide?) is common. Clans are hierarchical, with the pups of dominant females outranking the adult females subordinate to their mother--unless she dies.
Study of the spotted hyena gives us gnolls in matriarchal clans, who are fairly indistinguishable in terms of sex. There are probably some unusual--uh, physical characteristics of female gnolls--I'll leave it to individual GMs to work out the implications of those and how much game time they gets. On firmer ground for a game about killing things and taking stuff, gnolls probably eat their slain foes--bones and all. Also, competition is fierce within the clan, and only the strongest make it to adulthood.
So that's the current state of hyena knowledge, but there are some interesting things to be gleaned from outmoded/folkloric ideas. Take a look at this quote from T.H. White's translation of a twelfth century Latin bestiary, The Book of Beasts:
"[the hyena] is accustomed to live in the sepulchres of the dead and to devour their bodies. Its nature is that one moment is that it is masculine and at another moment feminine, and hence it is a dirty brute...it frequents the sheepfolds of shepherds and walks around the houses of a night and studies the tone of voice of those inside with a careful ear for it is able to do imitations of the human voice."Again there's the link between hyenas and the dead; between gnolls and ghouls, both under the demon-lord Yeenoghu's purview. But how do we make sense of the rest of it?
Well, maybe all gnolls are skilled vocal mimics. Perhaps their shaman's are gifted by their god to imitate the voices of others?
And the sex switch? Given the unclear separation of sexes among his people--and their matriarchal nature--I suspect Yeenoghu is a hermaphrodite, or perhaps genderless, but probably referred to by gnolls with a feminine pronoun (if their language has such a thing). Yeenoghu is a consummate trickster then, not even willing to stick to one gender. Possibly, gnoll shamans follow their god's/godess' lead and go by the pronoun of the other sex, symbolically becoming like their deity. Maybe hermaphrodites are especially holy?
There you have it: gnolls informed by hyenas in fact and folklore. Who'd of thought hyena-men could so easily out weird troll/gnome hybrids?