Você poderia fazer:
for file in fileA fileB; do
printf 'Records in %s are\n%s\n' "$file" "$(cat "$file")"
done > fileC
Ou:
for file in fileA fileB; do
echo "Records in $file are"; cat "$file"
done > fileC
Ambos produzem:
Records in fileA are
Hello
Records in fileB are
hi