ls | grep *.mp4

for a in *.mp4; do mv -n "$a" "${a/*/$RANDOM.mp4}"; done;  mv *.mp4 /home/misdeed/Documents

cd Documents; ls | grep *.mp4

a="This is name file"
echo $a

for file in *.mp4; do
  RANDOM_NAME="${file/*/$RANDOM.mp4}";
  mv -n "$file" /home/misdeed/Documents/"$RANDOM_NAME";
  echo "This is name $RANDOM_NAME.mp4";
done