What is the significance of the title Joe Turner's Come and Gone?

Quite simply, the significance of the title is in the title of a blues song with the same name:  "Joe Turner's Come and Gone."  Even though Joe Turner is not a character in this play, he is important in understanding these African-Americans in their quest for identity after slavery in that Joe Turner was the master who enslaved Herald Loomis.

We are introduced to the song (and the connection to the title of the play) "Joe Turner's Come and Gone" in the middle of the play when Bynum and Seth sit playing dominoes.  It is Herald Loomis who comes in and gets angry at the singing of the song.  Bynum pipes up and says that he knows Herald Loomis used to be one of Joe Turner's slaves and should remember the song.  This sparks a reverie by Herald Loomis about his enslavement to Joe Turner for seven long years.  After Loomis is released, Loomis has lost everything he holds dear:  his wife has left and his daughter has, too. 

In conclusion, the reader must understand that this song (and Loomis' experiece) is important both literally and metaphorically.  Loomis' story is important in itself in that Loomis is an important character; however, the story is also a metaphor for the entire slavery experience and the general African-American search for identity after the Civil War ended.  This, of course, continued into the 1900s which is when this piece of literature is set.