Joe, you're right as usual, however, I'm sure the other joe meant the dual rated THHN THWN, 'cuz I've seen no THHN that isn't rated THWN, and calling it the wrong thing doesn't make it lose its wet rating, correct?
The stuff I use says the following, maybe y'all use different stuff.
"GCC -W 12AWG VW-1 TYPE THHN OR THWN OR MTW (UL) 600 VOLTS GASOLINE AND OIL RESISTANT 11 OR AMW"
Could we just call it THHN and assume we're all talking about the same thing?
BTW, if I ask my supplier for THWN, they usually say "We don't carry that, but we can order it", then I'll say "Oh, just give me THHN instead."
I get exactly what I wanted in the first place!