The sa'ir, a forgotten monster

The sa'ir is a weird monster that appeared only briefly in 2e as part of the lamia’s ridiculously convoluted ecology (ridiculously convoluted ecologies were extremely common in the days of AD&D). It is a lion with a goat's hooves and horns. It was never referenced again, and 3e seemingly introduced male lamia which rendered its existence superfluous. That has not stopped conversions to 5e, however.

The name immediately stood out to me because I recognized it as probably derived from the biblical sa`iyr (also sâʻîyr, sâʻir). As an adjective the word means "shaggy," as a noun "he-goat." By analogy, the word is translated as "faun" or "satyr."

In Isaiah 34:14, the sa'ir ("wild goat") is mentioned alongside the lilith ("screech owl") as one of the many beasts inhabiting the desert and night. As Lilith is the name of a night-haunting demon in Mesopotamian myths that fulfills the same archetype as the lamia of Greek myth, I suspect this is where the game's writer got the idea to introduce the sa'ir as a monster related to the lamia/lilith.

Otherwise, the sa'ir appears to be an invention of the game's writer, derived from the biblical verse plus the lamia as described by Topsell and depicted in Tudor heraldry. However, there are a couple of heraldic and artistic monsters that loosely resemble it and might have influenced its design:

• The chatloup (French for "cat-wolf") is a fantastic beast with the face of a cat, the body of a wolf, and the horns of an antelope. 
• The theow (also thoye, thos) is a fantastic beast with the body of a mastiff or wolf, cloven hooves and a bovine muzzle and tail. Dragonlore #71 speculates that it was the result of careless copying transforming depictions of normal wolves into bovine beasts.
• The homeric Chimera was described as having the body of a goat, the head of a lion, and the tail of a dragon/snake. Further variations on this design might add horns to the lion's head.

I do not really see a reason to revive it as a relative of the lamia. At least in my campaign setting, the lamia are the transformed souls of scorned lovers in loose accordance with their mythological origins and not a self-reproducing race that arbitrarily serves a demon lord. Even in the biblical verse, it was only intended as one of the creatures inhabiting the same environment as the she-demons, not a relative.

I can imagine reviving it in other capacities, however. Maybe it is a mad wizard's experiment, as lazy game's writers are wont to resort to for explanation? Maybe it is a variant of the aberrant beasts spawned by the chimera? Maybe it is the male counterpart to the female chimera? Maybe it is a liocorno related to the bicorn and unicorn? Maybe it is related to the chatloup and theow, just another fantastic beast that is natural to fantasyland? Maybe, as its name suggests, it is a relative of the satyrs?

There are any number of possibilities.