Taidgazacaz,
On the same Census page as Pant Gnog in 1841 are Nant, Tynewydd, Shamber Wen, Llysy goed, Ty Newydd, Tyn y gaiau, Pentre Cilcen and Fron Fedw (as written by enumerator).
I can find all but Pant gnog and Fron Fedw on an 1879 Ordnance Survey map, North and North West of the village as you say.
Can't find Pant gnog in 1851 Census.
Tried to work out what gnoch/cnoch or gnog/cnog might be no success.
regards