Libel is slander intended to defame. When (((they))) are accused of the ritual murder of Christians, (((they))) refer to those accusations as blood libel.
(((They))) performed a ritual murder on St. Simon of Trent, and to this day, (((they))) shriek about blood libel whenever their history of ritual murder is brought up.
"Libel" has referred to a formal statement or accusation for approximately 700 years. The "new" connotation of that accusation being false has been around for almost 400 years. Again, words mean things.