Lopping through a data frame and calling variables within the data frame?

I am looping through each of the data frames in my code and then attempting to change some variables within each data frame.

I am essentially unsure how to handle the portion calling the variable:

dates <-mdy(paste0(i,$orig_dt))

This shows an error of unexpected '$'.

Here is the whole code:

 for (i in names(which(unlist(eapply(.GlobalEnv,is.data.frame))))) {
  names(i) <- tolower(names(i))
  #Parse Month
  dates <-mdy(paste0(i,$orig_dt))
  i <- i %>%
  mutate(orig_dt = mdy(orig_dt),
          Month = month(orig_dt, label = T),
          Year = year(orig_dt),
          Date = mdy(paste0(Month,"/01/",Year)))