| floor(noun, support, base, foundation, bed) |
| footing(noun, support, cause, start, substance) |
| groundwork(noun, support, cause, start, thing) |
| keister(noun, buttocks) |
| low(noun, adjective, close, decline, low) |
| tush(noun, part, end, back, slang) |
| underlying(adjective, important, original, basic, vital) |
| anus |
| cause(noun, feeling, start, energy, spirit) |
| found(verb, support, hold, maintain, stay) |
| last(noun, adjective, property, fundamental, lowest) |
| lowermost(adjective, fundamental, over, lowest, nethermost) |
| nethermost(adjective, fundamental, over, lowest) |
| rock-bottom(noun, adjective, fundamental, collateral, subalternate) |
| root(noun, verb, adjective, support, quality) |
| substance(noun, quality, feeling, cause, start) |
| tail end(noun, expression, idiom, back, top) |
| underpinning(noun, support, cause, start, substance) |
| ass |
| asshole |