The story
First used by NASA mission specialist Robert W. Farquhar in 1966 for calculated orbits around the Earth–Moon L₂ point which required the use of thrusters to be made periodic.
Etymology from Wiktionary, CC BY-SA 4.0.
halo orbit
Today it means: A periodic, three-dimensional orbit about any one of the Lagrange points L₁, L₂ or L₃ of a two-body gravitational system. Full definition →