Bem, vamos dividir isso em etapas simples:
#!/bin/bash
# First, let's get that file's name:
FILE=$(ls -rt ORIGFILE*.txt | tail -n1)
if [[ 0 -ne $? ]]; then
echo "Unable to locate matching file. Aborting." 1>&2
exit 1
fi
# Now, create a new file containing the file's name:
echo "$FILE" > NEWFILE.TXT
# And append the contents of the old file into the new:
cat "$FILE" >> NEWFILE.TXT
# Finally, get rid of the old file: (uncomment if you're sure)
# rm "$FILE"