Totally understand the ITIL V3 framework is not equal to Application Development Lifecycle. I need to understand if “errors” are equal to “defects” from a nomenclature perspective.
ITIL is intended for IT services. Usually, services are relying on application so you can drive the parallel between IT service lifecycle and application lifecycle. The article "ITIL Application Management Function – Custodian of application knowledge" https://advisera.com/20000academy/blog/2014/03/18/itil-application-management-lifecycle-within-service-lifecycle/ can help you with this.
Defects vs. errors - well, defects are qualiyt management description of nonconformity related to the specified use. ITIL doesn't use word defect but error if there is a discrepancy between what an service should do and what it does. Corrective action follows defect and errors are followed by change.