ETL
From Just Solve the File Format Problem
ETL (Event Trace Log) files store the output of instruments attached to their application, or user or kernel events during real-time. The enable the consumption of those events post- that time.
According to file.org these files "can contain information about disk access and page faults, logging high-frequency events and recording the performance of the Microsoft operating system. This information can be used to analyze and adjust voice response software applications."
