The phrase “something is rotten in Denmark” originates from William Shakespeare’s play Hamlet. In the play, the character Marcellus says, “Something is rotten in the state of Denmark,” to express his suspicion that something is amiss or wrong in the kingdom, particularly in relation to the mysterious death of the king and the subsequent events.
Over time, the expression has come to mean that something is suspicious, corrupt, or not quite right in a situation or organization. It suggests that there is a hidden issue or corruption that has yet to be uncovered.