Usage: 2 forms in 4 verses
Form Translated As     In Verse(s)
ορκισμού Oath LXX.Gen.21.32
my oath LXX.Gen.24.41
of Oath LXX.Gen.21.31
ορκίσμου of conjuring LXX.Lev.5.1

Liddell-Scott-Jones

ὁρκισμός (horkismos) a conjuring G:N-M

ὁρκισμός-ισμός, ,

administration of an oath, [LXX+2nd c.BC+]; probably falsa lectio for{ὁρισμός}, = sponsio, in [Refs 1st c.AD+]

LSJ Scripture Refs: LXX.Gen.21.31