What does ETOC stands for?
The TOC stands for Table of Contents and the e refers to the electronic/digital way of displaying the table of contents. This is the only thing I could find about this on the Google Search engine. It's also related to the backup storage and various technologies related to this.
Access the following link to obtain additional data: https://www.ibm.com/support/knowledgecenter/en/SSGSG7_6.4.0/com.ibm.itsm.client.doc/r_opt_toc.html