pandas replace duplicates unique identifier

1import pandas as pd
2import numpy as np
3data = {'Name':['Tom', 'Tom', 'Jack', 'Terry'], 'Age':[20, 21, 19, 18]} 
4df = pd.DataFrame(data)
5
6nth = ['First', 'Second', 'Third', 'Fourth']
7
8def prefix(d):
9    n = len(d)
10    if n > 1:
11        return d.radd([nth[i] for i in range(n)])
12    else:
13        return d
14
15df.assign(Name=df.groupby('Name').Name.transform(prefix))
16
17          Name  Age
180     FirstTom   20
191    SecondTom   21
202         Jack   19
213        Terry   18
22​
23