I must correct myself.
"(8) A plausible explanation of how Big Bend came to be named in versions of the ballad is that it stems from "big bad tunnel" (found in at least one version), which could be a reference to "long" (Coosa) tunnel, which gave much grief in the construction of the C & W (compare "C & O"). Nelson posits that the John Henry incident, whatever he thinks it might have been (which is not clear), occurred at Lewis Tunnel but was first sung about it at Big Bend. Why this should be is not clear."
My leaky memory failed me. I'm not sure that any version of "John Henry" has been collected that contains "big bad tunnel." One of Chappell's versions (XXX, from Hattie Kelley, Jefferson, NC, written copy) contains "Big Band tunnel on the C and O road." Hattie, probably, was a poor speller and intended "Big Bend." However, this triggered my speculation that "big bad tunnel" could mutate readily to "Big Bend Tunnel." That an early version contained "big bad tunnel" (referring to Coosa Tunnel) is a plausible speculation, but it remains nothing more than that. I wish I *could* find a version with "big bad tunnel."