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backside base basement basis bed bedrock behind boat buttocks butting bum butted in butt butt crafts craft depended depend depth derriere derriere/derrière essence fanny footing foot foundations found foundation fundament fundamental ground hinge on hinging on hollow hinges on inferior keister/keester least lesser low lowest marrow meat and potatoes minimum most fundamental more primary most inferior most primary nadir pedestal posterior primary/prime primest quintessence radical rear reverse rest rest rock bottom root rudiment seat seat setbacks side slump souls soul stuff substance substratum substances support supports tail underneath underneath under underside underlying valleys valley vessel zero