| root(noun, cause, base, source, core) |
| radix(cause, quick, source, root, origin) |
| starting point(expression, cause, quick, root, origin) |
| beginnings(cause, quick, source, origin, stem) |
| bulb |
| center(cause, source, root, origin, mainspring) |
| core(cause, source, root, origin, mainspring) |
| mainspring(cause, quick, source, root, origin) |
| marrow(cause, source, root, origin, mainspring) |
| quick(cause, source, root, origin, stem) |
| rhizome(cause, quick, source, root, origin) |
| rock bottom(expression, cause, quick, source, origin) |
| sperm |
| tap |
| taproot |
| tuber(cause, quick, source, origin, stem) |
| tubercle |
| base(cause, source, origin) |
| basis(cause, source, origin) |
| bedrock(cause, quick, source, origin, stem) |