Let us say you have few files to be renamed and you would like to rename the files in bulk. Old names and new names are present in two columns in a separate file and are separated by tab (or any delimiter that is unique between two columns). 

Example file:

Old_file    New_file
boomer    genZ

You can change the file names in  multiple ways:

1. awk -v OFS=" " '{print "mv",$1,$2}' file.txt| sh
2. while IFS=$'\t' read old new; do echo mv $old $new;done < test.txt