Rhoda, from the Greek word pronounced roe-dose (the Greek island Rhodes takes its name from the name Greek word), meaning a rose, was a young Christian girl who was among those at "the house of Mary the mother of John, whose surname was Mark; where many were gathered together praying" (Acts 12:12 KJV) for protection from Herod's deadly persecution. Rhoda was the first to discover that their prayers were being answered - she found the rescued apostle Peter at the door.
"And as Peter knocked at the door of the gate, a damsel came to hearken, named Rhoda"
There are four men of Bible History who were known as Herod (see the Fact Finder question below). Herod Agrippa I was the son of Aristobulus and Bernice, and grandson of Herod The Great (the Herod who tried to murder Christ when He was born). Herod Agrippa I was tetrarch of the provinces previously ruled by Lysanias II, but eventually he possessed the entire kingdom of his grandfather, with the title of king. It was Herod Agrippa I that had James, the brother of John, martyred. He then imprisoned Peter with the intention of killing him also, but God had an angel go in and get him out (see below). Like all of the rest, Herod Agrippa I had a very high opinion of himself until one day, about 44 A.D., it went too far. He claimed to be divine, and The Lord struck him down.
"12:21 And upon a set day Herod, arrayed in royal apparel, sat upon his throne, and made an oration unto them. 12:22 And the people gave a shout, saying, It is the voice of a god, and not of a man. 12:23 And immediately the angel of the Lord smote him, because he gave not God the glory: and he was eaten of worms, and gave up the ghost" (Acts 12:21-23 KJV)
Herod's deadly attacks on the Church of God before that however began with the killing of "James the brother of John with the sword" (see also What Happened To The Apostles?). Peter was the next intended victim.
"12:1 Now about that time Herod the king stretched forth his hands to vex certain of the church [see also What Is The Church?]. 12:2 And he killed James the brother of John with the sword. 12:3 And because he saw it pleased the Jews, he proceeded further to take Peter also. Then were the days of unleavened bread [see The True Christian Holy Days: Lesson 2]. 12:4 And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter [Note: "Easter" in this verse is an error by the King James Version translators; the actual word that was originally written in the Holy Scriptures is Passover, as most other translations correctly render it] to bring him forth to the people.
The time of Peter's Ministry was not yet over however. Peter would eventually be martyred (see the Fact Finder question below), but at a time of The Lord's choosing, not any man.
"12:6 And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison. 12:7 And, behold, the angel of the Lord came upon him, and a light shined in the prison: and he smote Peter on the side, and raised him up, saying, Arise up quickly. And his chains fell off from his hands.
Rhoda was the first to discover Peter's freedom.
"12:12 And when he had considered the thing, he came to the house of Mary the mother of John, whose surname was Mark [see John Mark]; where many were gathered together praying. 12:13 And as Peter knocked at the door of the gate, a damsel came to hearken, named Rhoda. 12:14 And when she knew Peter's voice, she opened not the gate for gladness, but ran in, and told how Peter stood before the gate.
Fact Finder: Did Peter know that he would eventually be martyred? How did he know? Who told him?