Gist to illustrate the insertion of first element on nested list.

insert_name.py

# Import copy lib
import copy

# Create lists:
names = ["Mary", "David", "George"]
numbers = [[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]]

# Create a deep copy to avoid using same memory direction:
new_list = copy.deepcopy(numbers)

# Insert elements as wanted:
for i in new_list:
    i.insert(0, names[0])

# Print (the one edited) new list:
print(new_list)

# We can compare with the original list:
print(numbers)