I am, also, a huge J. R. R. Tolkien fan. I’ve read everything he wrote at least two times (LOTR uncountable times). Particularly, I have the greatest respect for the Mithology he created, and tend to pay strong attention to details.
Nardol was the third of the Warning Beacons of Gondor, that ran between Minas Tirith and Rohan, and served as an alarm system that any of the two people could trigger once under attack.
The first two were Amon Dîn, and Eilenach, and the four others were Erelas, Min-Rimmon, Calenhad, and Halifirien. Nardol, though, was different from the six others, for the
summit of that mountain [Eilenach] came to a sharp point, making the building of a bright beacon difficult. The next Beacon site to the west was not so hampered – it stood on the broad end of a ridge of the White Mountains, and the guard station maintained there could create a huge signal fire when needed. It was for this reason that the third Beacon acquired the name Nardol, “fire-hilltop”, because its beacon-fire was so bright it could be seen more than a hundred miles away
according to The Encyclopedia of Arda.