One of the mysteries of the English language finally explained.
Definition of recidivation in US English:
recidivation
noun
1The action of relapsing into sin or error; backsliding, apostasy. In later use: specifically = "recidivism".
2Medicine. Recurrence (of a disease, symptom, or condition); relapse; an instance of this. Now rare.
Origin
Late Middle English; earliest use found in Richard Rolle (a1310–1349), hermit and religious author. From post-classical Latin recidivation-, recidivatio (in medical context) recurrence, relapse, action of relapsing into sin or error from recidivat-, past participial stem of recidivare + classical Latin -iō.