Per the AD&D 1e MM, they were like other humanoids1
While Original D&D didn’t go into this kind of detail (and thus the question’s answer is mu for that edition) the AD&D 1e MM treated them the same way as most giant class creatures (which was most of the humanoids plus ogres, ettins, trolls, and giants2).
In the second paragraph of the MM entry on gnolls, we find:
The lair will also contain females and young equal to 50% and 200%
respectively of the number of males present (MM, p. 46)
See this similar entry for goblins
… females and young equal to 60% and 100% respectively of the number of male goblins encountered (MM, p. 47)
And this entry for orcs
… females equal 50% of the number of males, young equal to 100% of
the number of males (MM, p. 76)
Entries for bugbears, hobgoblins and ogres are similar. In that respect, when the game first treated them as more than an entry on the monster’s appearing table (Original D&D) they were certainly what D&D 5e would class as a humanoid like a hobgoblin or an orc, with their lair being populated by mates and young in varying proportions to the male population.
From the above we can infer, with confidence, that they reproduced like other humanoid creatures for that edition.
Yeenoghu was a demon, stats as a monster
It is worth noting that the first exposition on the gnoll deity Yeenoghu he was a “demon lord” in the MM; as a deity, he arrives in a book published three years after the MM, Deities and Demigods but they didn’t go into much detail in that entry, basically telling the DM “see the MM”.
I’ll compare that treatment to AD&D 2e’s MM when I am where I can access it. May be a day or two. Somewhere along the line, their connection with hyenas (which is alluded to in the AD&D 1e MM) was expanded upon.
From the 3.5 SRD, they are certainly painted as something a lot different from the other humanoids:
A gnoll is a nocturnal carnivore, preferring intelligent creatures
for food because they scream more.
As I no longer have my 3.5 MM, I’ll just leave that there as a pointer to differentiating them from the goblins, orcs, and hobgoblins who are a lot more like humans that gnolls were.
1 In 1e ‘humanoid’ applied to orcs, bugbears, gnolls, goblins, etc and ‘demi human’ applied to halflings, elves, gnomes, dwarves, etc).
2Giant class creatured, per PHB p. 24 (Ranger description) were bugbears, ettins, giants, gnolls, goblins, hobgoblins, kobolds, ogres, ogre magi, orcs and trolls. The ranger had bonus to damage against these kinds of creatures, an early version of ‘favored enemy’ of 5th edition).