The dura mater continues as an extension called the filum terminale, which anchors the spinal cord to the coccyx.
From the en.wikipedia.org
Not a filum for adults to review?
From the guardian.co.uk
When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while.
From the en.wikipedia.org
The human spinal cord extends from the foramen magnum and continues through to the conus medullaris near the second lumbar vertebra, terminating in a fibrous extension known as the filum terminale.
From the en.wikipedia.org
More examples
Filament: a threadlike structure (as a chainlike series of cells)
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain (the medulla specifically). The brain and spinal cord together make up the central nervous system. ...
A filamentous anatomical structure
Latin = a thread. Filum terminale - a thread of pia continuous with the lower end of the spinal cord.