evolute

noun

evo·​lute ˈe-və-ˌlüt 

 also  ˈē-və-

: the locus of the center of curvature or the envelope of the normals of a curve

Word History

Etymology

borrowed from New Latin ēvolūta (short for līnea ēvolūta, literally, "unrolled line"), noun derivative from feminine of Latin ēvolūtus, past participle of ēvolvere "to roll out or away, unwind, unroll" — more at evolve

Note: The New Latin term was introduced by Christian huygens in Horologium oscillatorium (Paris, 1673), p. 60.

First Known Use

1704, in the meaning defined above