Holdfast
Holdfast , noun
1.
Something used to secure and hold in place something else, as a long flat-headed nail, a catch a hook, a clinch, a clamp, etc.; hence, a support.
His holdfast was gone.
2.
(Botany) A conical or branching body, by which a seaweed is attached to its support, and differing from a root in that it is not specially absorbent of moisture.