Why is Satan called the "Accuser"?

He is called the Accuser of the Brethren because he goes before the Father and makes lying accusations against Christians all day long. (Revelation 12:10)

He will accuse each person of his sins upon dying and on Judgement Day.

The name Satan means "Accuser". That is what Satan does, he accuses us before God.

Revelation 12:10“And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.”

[7] And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,

[8] And prevailed not; neither was their place found any more in heaven.

[9] And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.

[10] And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.            Rev 12

 Is this to say that wickedness originated entirely with humans? No, there is more to it. The creation of intelligent creatures was not limited to humans. Already God had created countless spirit creatures in the heavens. (Job 38:4, 7) They too were free agents and also had a choice in accepting their Creator’s direction. One of those spirit creatures chose to dwell on a desire for independence. His ambition built up to such a degree that it moved him to challenge God’s authority. He told Adam’s wife, Eve, that they could break God’s law and yet, as he assured her, “You positively will not die.” (Genesis 3:4; James 1:13-15) His statements implied that they did not need their Creator in order for them to have continued life and happiness. In fact, he said that lawbreaking would actually improve matters for them, enabling them to be like God. Thus he called into question the validity of God’s laws and cast doubt on God’s way of governing them. Indeed, he cast doubt on their Creator’s very right to rule. For this misrepresentation he came to be called Satan, which means “resister,” and Devil, meaning “slanderer.” For the past 6,000 years this attitude of Satan has influenced mankind, advancing a policy of ‘rule or ruin.

Enki in Akkadian . Smart god Enki was .

Being called accuser is derogatory used in spin called " Accuse of known Guilt " .

Skydaddy does that when she accuses you of sinning and falling short . that is telling .

 It tells me most likely she is short , round and a butterface to boot so that short round stuff must be holy after a dude has been up there a few hundred years 

The Book of Job can help with understanding why. When Satan finds a righteous person, he begins knit-picking his life apart to find something that he can use against the person in order to destroy him. If that fails, he sets up traps to provoke the person into sin, causing pestilence and destruction to fall upon him, sowing discord and division, isolating the person and dragging him to the lowest depths possible, so that he breaks. Once the person is broken and in shambles, Satan accuses him before God, tempting his death. In this world, Satan is the prosecutor, Jesus is the defense attorney, God is the judge, and man is the accused.

Satan, using people, has hurled false accusations against Jesus and his Father for centuries.  It continues down to this day as again, using people, accusations have been hurled against those who follow what the Bible says.  I was just reading an article about how Russia is imprisoning those who practice their faith, calling them extremists.