For a common words, it’s used sparingly, so we can’t say anything robust about its absence from some of the Chapters – but it is in Gollum’s chapter and not Smaug’s?? Fascinating.

• 1.064 Smash the bottles and burn the corks!
• 2.080 (and two with burns
• 3.013 They were burning bright
• 3.040 and the burned banks of the bright River Running.
• 4.036 The sparks were burning holes
• 4.041 It burned with a rage that made it gleam
• 5.101 the light of his eyes burned with a pale flame.
• 6.065 and burned into them,
• 6.065 while those that were burning were running about howling
• 6.077 Burn, burn tree and fern!
• 6.077 Burn, burn tree and fern!
• 6.083 and the burning,
• 6.085 Soon the light of the burning was faint below,
• 7.045 Though it was summer there was a wood-fire burning
• 7.106 The fire burned low
• 7.122 From the burnt wolf-glade
• 7.122 and also because of the burning
• 8.048 and fires burning on the ground;
• 8.054 and fires were burning under the trees,
• 10.035 The lakes shall shine and burn,
• 13.044 and half burnt.
• 14.013 and their shafts fell back kindled by his breath burning
• 14.016 and burned down to the surface of the lake.
• 14.018 that held their ground among the burning houses.
• 17.038 burned
• 18.001 but his head burned with fire.
• 19.004 The stars are all burning!

My luck would run ill, I fear, if I left out a few words: “Wee, sleekit, cow’rin, tim’rous beastie, O, what a panic’s in thy breastie!”