Siding

wiktionary

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side +‎  -ing(“material, collection”). 

siding

side +‎  -ing(“derivative noun, having the quality of”). 

etymonline

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siding (n.)

c. 1600, "a taking of sides in a conflict or debate," verbal noun from side. First attested 1825 in the railroad sense; 1829, American English, in the architectural sense of "boarding on the sides of a building."