I have a this data set as sample:
df = pd.DataFrame({'CL1':['A B C','C A N']},
                columns=['CL1','CL2','CL3','CL4']) 
  
     CL1  CL2  CL3  CL4  
0  A B C  NaN  NaN  NaN  
1  C A N  NaN  NaN  NaN  
 
         
My Goal:Finding of most repetition of words combination in data frame with following steps.
- 
- Make a separation of each value with (,) as separator and add in column CL2:
 
- Make a separation of each value with (,) as separator and add in column 
     CL1     CL2     CL3  CL4 
0  'A B C'  'A,B,C'  NaN  NaN 
1  'C A N'  'C,A,N'  NaN  NaN 
- 
- Separation of value in columns CL2in columnCL3:
 
- Separation of value in columns 
     CL1     CL2     CL3          CL4 
0  'A B C'  'A,B,C'  'A','B','C'  NaN 
1  'C A N'  'C,A,N'  'C','A','N'  NaN 
     
- 
- Union (set theory from statistic) of column CL4
 
- Union (set theory from statistic) of column 
     CL1     CL2     CL3          CL4 
0  'A B C'  'A,B,C'  'A','B','C'  [ [A],[B],[C],[A,B],[A,C],[B,C],[A,B,C] ] 
1  'C A N'  'C,A,N'  'C','A','N'  [ [C],[A],[N],[A,C],[C,N],[A,N],[C,A,N] ] 
       
- 
- Finding of the repetition of each value of column CL4in new columnCL5in new data frame and add toCount:
 
- Finding of the repetition of each value of column 
     CL5      Count   
0    [A]       2
1    [B]       1
2    [C]       2
3    [D]       1
4    [N]       1
5    [A,B]     1
etc..
 
    