This one might need explanation. This old folk song had different verses people would sing, so there were basically different versions. A popular set was:

She’ll be comin’ around th mountain, when she comes
She’ll be comin’ around th mountain, when she comes
She’ll be comin’ around th mountain
She’ll be comin’ around th mountain
She’ll be comin’ around th mountain, when she comes

She’ll be drivin’ six white horses, when she comes
She’ll be drivin’ six white horses, when she comes
She’ll be drivin’ six white horses
She’ll be drivin’ six white horses
She’ll be drivin’ six white horses, when she comes

O, we’ll all go out an’ meet ‘er, when she comes
O, we’ll all go out an’ meet ‘er, when she comes
O, we’ll all go out an’ meet ‘er
O, we’ll all go out an’ meet ‘er
O, we’ll all go out an’ meet 'er, when she comes

O, we’ll kill the old red rooster, when she comes
O, we’ll kill the old red rooster, when she comes
O, we’ll kill the old red rooster
O, we’ll kill the old red rooster
O, we’ll kill the old red rooster, when she comes

And, we’ll all have chicken an’ dumplins, when she comes
And, we’ll all have chicken an’ dumplins, when she comes
And, we’ll all have chicken an’ dumplins
And, we’ll all have chicken an’ dumplins
And, we’ll all have chicken an’ dumplins, when she comes

Like a lot of songs for kids, people often added a callback response at the end of every line (in this case, after each time it says “when she comes”). The one for the verse about killing the old red rooster was “whack whack whack.”