itare.saam - what does it mean?

[Dmitri]

Dear INDOLOGY members!

Here is a question I try to find a satisfactory answer to:

What is the meaning of Sanskrit word itare.saam (YogaS. I.20)?
Translation usually given in renderings of YogaS. is
"other" "of other" which does not look satisfactory at all.

1. It might be fem.sing.acc of itare.saa which would then
    be derived as "itara-i.s-aa" or "itara-ii.s-aa"
2. It might be pl.gen. of consonantal stem itare.s which then would
   be derived as "itara-i.s" or "itara-ii.s"

Since itara already means "the other (of the two), another"
translation "itare.saam" as "of other" or "other" would ignore
the "i.s" or "ii.s" part.

Any ideas about the meaning of "itare.saam" ?
Any knowledge of conventional use of it?

Thanks all responding to my previous questions!
TIA,  Dmitri.