More efficient way to create frequency column based on different groupings

I have code below that calculates a frequency for each column element (respective to it's own column) and adds all five frequencies together in a column. The code works but is very slow and the majority of the processing time is spent on this process. Any ideas to accomplish the same goal but more efficiently?

Create_Freq - function(Word_List) {

 library(dplyr)
 
 Word_List$AvgFreq - (Word_List%% add_count(FirstLet))[,n] +
                      (Word_List%% add_count(SecLet))[,n] +
                      (Word_List%% add_count(ThirdtLet))[,n] +
                      (Word_List%% add_count(FourLet))[,n] +
                      (Word_List%% add_count(FifthLet))[,n]

 return(Word_List)
}

```