Merge related words in NLP

I'd like to define a new word which includes count values from two (or more) different words. For example:

Words Frequency
0   mom 250
1   2020    151
2   the 124
3   19  82
4   mother  81
... ... ...
10  London  6
11  life    6
12  something   6

I would like to define mother as mom + mother:

Words Frequency
0   mother  331
1   2020    151
2   the 124
3   19  82
... ... ...
9   London  6
10  life    6
11  something   6

This is a way to alternative define group of words having some meaning (at least for my purpose).

Any suggestion would be appreciated.

from Merge related words in NLP