Kitto's Popular Cyclopedia of Biblial Literature
The original word, which bears this leading signification, means—1. One who has a cause or matter of contention; the accuser, opponent, or plaintiff in any suit (Judges 12:2; Matthew 5:25; Luke 12:58). We have little information respecting the manner in which causes were conducted in the Hebrew courts of justice, except from the Rabbinical authorities, who, in matters of this description, may be supposed well informed as to the later customs of the nation. Even from these we learn little more than that great care was taken that, the accused being deemed innocent until convicted, he and the accuser should appear under equal circumstances before the court, that no prejudicial impression might be created to the disadvantage of the defendant, whose interests, we are told, were so anxiously guarded, that any one was allowed to speak whatever he knew or had to say in his favor, which privilege was withheld from the accuser. The word is also applied in Scripture, in the general sense, to any adversary or enemy (Luke 18:3; 1 Peter 5:8). In the latter passage there is an allusion to the old Jewish opinion that Satan was the accuser or calumniator of men before God (Job 1:6, sq.; Revelation 12:10, sq.; comp. Zechariah 3:1). In this application the forensic sense was still retained, Satan being represented as laying to man's charge a breach of the law, as in a court of justice, and demanding his punishment [SATAN].
Kitto, John, ed. Entry for 'Accuser'. "Kitto's Popular Cyclopedia of Biblial Literature". https://www.studylight.org/encyclopedias/eng/kbe/a/accuser.html.