Foggy Mountain Top is one of teh Carters well known songs. Earl Skruggs formed his own group, the Foggy Mountain Boys, which was named this song.

The song Rocky Mountain Top is the basis for the Carters:
http://www.traditionalmusic.co.uk/english-folk-songs/southern-appalachians%20-%200305.htm

I have another version of Rocky Mountain Top in my edition. Randolph collected a version as did Brown. It's hard to tell if the Carters song was the basis for songs collected after 1940. The JOAFL 1945 has the text.

The song is related to the false Young Man songs: White Oak Mountain
and Rocky Mountain Side. The Carters are a collection of floating lyrics.

FOGGY MOUNTAIN TOP- Carter Family 1929

          If I was on some foggy mountain top
          I'd sail away to the west
          I'd sail around this whole wide world
          To the girl I love the best

          If I had listened what mama says
          I would not have been here today
          A-lying around this old jail house
          A-weeping my sweet life away

               Yeah, oh-lay-ee-oh, lee-oh-la-ee-ay
               Lee-oh-lay-ee, lay-ee, oh-lay-ee

                [INSTRUMENTAL BREAK]

          Oh, if you see that girl of mine
          There's something you must tell her
          She need not be foolin' no time away
          To court some other feller

          Oh, she's caused me to weep, she's caused me to mourn
          She caused me to leave my home
          For the lonesome pine and the good old times
          I'm on my way back home

               Yeah, oh-lay-ee-oh, lee-oh-la-ee-ay
               Lee-oh-lay-ee, lay-ee, oh-lay-ee
                [INSTRUMENTAL BREAK]

          Oh, when you go a-courtin'
          I'll tell you how to do
          Pull off that long-tailed roustabout
          Put on your navy blue

               Yeah, oh-lay-ee-oh, lee-oh-la-ee-ay
               Lee-oh-lay-ee, lay-ee, oh-lay-ee
                [INSTRUMENTAL BREAK]