🔼The name Jabbok in the Bible
The river Jabbok starts in the mountains of Gilead and pours out into the Jordan, from the east. Its modern name is Wadi Zurkah, which means Blue River. In the Bible the river Jabbok is most pronounced for being the river on which banks Jacob encounters the Angel of YHWH, and is transformed from being a person named Jacob to a nation named Israel (Genesis 32:22).
When Israel has become a nation on the move, the Israelites send a message to king Sihon of the Amorites, stating that they want passage through his realm. Sihon objects to such a logistical nightmare and decides to attack Israel in stead. That quickly proves to be bad thinking, because Israel defeats his army and takes possession of his land from the Arnon to the Jabbok (Numbers 21:24).
The Ammonites, however, remain angry that Israel has taken possession of Sihon's turf, and start bothering people in the border region. The judge Jephthah starts diplomatic peace negotiations and explains to the Ammonites that they never just took the land, but were attacked and conquered their enemy, or in other words: the Lord gave them the land. That explanation results in more war, a lot of dead Ammonites, and Jephthah's foolish vow that cost his daughter her life as she knows it (Judges 11).
🔼Etymology of the name Jabbok
The name Jabbok comes from the root-group בקק:
For a meaning of the name Jabbok, NOBSE Study Bible Name List proposes Luxuriant River, and Jones' Dictionary of Old Testament Proper Names suggests Emptying or Pouring Out.
It should be noted that the Blue River now and the Jabbok back then most likely too, is a rapid, torrential river, and either of the above mentioned translations is valid.
BDB Theological Dictionary doesn't translate this name, but states that it is indeed "probably" derived from בקק. BDB additionally makes the valid observation that our name might also be connected to the verb אבק ('abaq), which is usually translated with to wrestle, but which is in fact reserved to the highly enigmatic encounter that Jacob had with the angel at the Jabbok (Genesis 32:24-25).