1) Unilateral comes from “uni” meaning one. Like a unicycle: this is an “Unconditional Covenant” because it is one-sided.
2) Bilateral comes from “bi” meaning two. Like a bicycle: this is a “Conditional Covenant” because each persons promise is dependent on the other.
The Hebrew word for Covenant is “Berith”. This most likely comes from “bara” meaning “to cut”, as Abraham cut the animals in two to prepare God’s covenant in Gen. 15. This is most likely were we understand the term “blood covenant”.
So, a blood covenant symbolizes “life” or more likely “death”. Some say this was communicating, may my blood be required of me if I do not uphold this bond.
A covenant is a confirmed “promise”. This was usually associated with either witnesses, or symbols to establish the promise. God called this a confirmed oath.
Heb. 6 “13 For when God made a promise to Abraham, because He could swear by no one greater, He swore by Himself, 14 saying, “Surely blessing I will bless you, and multiplying I will multiply you.”[d] 15 And so, after he had patiently endured, he obtained the promise. 16 For men indeed swear by the greater, and an oath for confirmation is for them an end of all dispute. 17 Thus God, determining to show more abundantly to the heirs of promise the immutability of His counsel, confirmed it by an oath, 18 that by two immutable things, in which it is impossible for God to lie, we might[e] have strong consolation, who have fled for refuge to lay hold of the hope set before us.