lucus a non lucendo

lu·​cus a non lu·​cen·​do

ˈlükəˌsā¦nänlüˈsenˌdō

: an illogical explanation or absurd derivation : non sequitur

the whole discussion may seem a lucus a non lucendo for all the light it throws upon the effect of the classics on mediaeval literature

—H. O. Taylor

Word History

Etymology

New Latin, a grove from not being light; from the practice ascribed to ancient Roman etymologists of deriving words from their semantic opposites, as lucus ("grove") from lucēre ("to shine, be light") because a grove is not light

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