The quality or state of being droll; the character of being amusingly odd, whimsical, or cleverly funny.
From 'droll' (adjective) with the abstract noun suffix '-ness,' which converts adjectives into nouns indicating a quality or state. Standard English morphology for creating abstract nouns.
The '-ness' suffix is so efficient that 'drollness' packed in the whole concept of sophisticated, unexpected humor into a single word that Victorians loved.
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