different between gallingly vs fallingly

English

galling +? -ly

gallingly (comparative more gallingly, superlative most gallingly)

falling +? -ly

fallingly (comparative more fallingly, superlative most fallingly)

While falling; with a falling motion.
- 1915, Jack London, The Little Lady of the Big House
  Here, in distress that was consternation, and in fear that was panic, excitedly bobbed up and down a cowboy in bearskin chaps, vacuously repeating the exclamation, "Oh God! Oh God!" — the first division of it rising in inflection, the second division inflected fallingly with despair.

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