The name Adoni-bezek in the Bible
Adoni-bezek is probably not really a personal name but rather a royal title—not unlike Pharaoh or Candace—namely that of the king of Bezek when the men of Judah and Simeon set out to conquer the lands allotted to them (Judges 1:5).
This Adoni-bezek had the habit of cutting off the thumbs and big toes of conquered kings, and having up to seventy of them scurry around under his table hunting for food. When Judah and Simeon sacked Bezek and captured Adoni-bezek they did to him the same and afterwards they took him to Jerusalem.
Adoni-bezek died there but it's not clear whether he died because of the treatment he received, or of old age, or because Judah and Simeon proceeded to massacre the townsfolk of Jerusalem and set fire to their city.
Etymology of the name Adoni-bezek
The name Adoni-bezek consists of two elements. The first part of our name is similar to the familiar Hebrew word אדנ (adan), roughly meaning Lord:
The post-fixed letter י (yod) creates a possessive form: אדני (adoni), means my lord, or lord of, depending on the context.
The second part of the name Adoni-bezek comes from the word בזק (bezek), meaning lightning:
The whole name Adoni-bezek would thus mean Lord Of Scattering or Lord Of The lightning Bolt.
Another name that means lightning is Barak.