SOED CD ROM (20 yrs old) re precarity - not in

precarium /prI"kE:rIm/ n. Pl.
[L, use as n. of neut. of precarius: see PRECARIOUS.] Rom. & Sc. Law. A loan granted on request but revocable whenever the owner may please.

But instantiate is:
Represent by an instance.

though it would seem in code writing the meaning doesn't now imply as an example. ie it was used before (≈ precedent set)