The meaning of the song "I've been working on the railroad"

I've been working on the railroad
All the livelong day
I've been working on the railroad
Just to pass the time away

Can't you hear the whistle blowing
Rise up so early in the morn
Can't you hear the captain shouting
Dinah, blow your horn

Dinah, won't you blow
Dinah, won't you blow
Dinah, won't you blow your horn
Dinah, won't you blow
Dinah, won't you blow
Dinah, won't you blow your horn

Someone's in the kitchen with Dinah
Someone's in the kitchen I know
Someone's in the kitchen with Dinah
Strumming on the old banjo, and singing

Fie, fi, fiddly i o
Fie, fi, fiddly i o
Fie, fi, fiddly i o
Strumming on the old banjo

Some people believe that this song was created by African-Americans who were working on the railroad at the time.  Often, the workers or slaves would sing a song to pass the time.  There are a lot of different opinions about this song and where it came from.  I believe in my own opinion that it was made while working on the rail road. 

 https://www.youtube.com/watch?v=CkQQbRqLoCI