accuse falsely, slander, libel
讕 centers on making false damaging statements about someone: accusing falsely, slandering, or committing libel.
讕 combines 言 (speech) with 闌, which likely contributes the sound and may relate to obstruction or blocking, suggesting speech that blocks or harms someone's reputation.
Words 言 that block or obstruct 闌 someone's good name: false accusations and slander.
For ラン, imagine a slanderer running their mouth: run -> ラン, and the false words spread quickly.