章動

Etymology
So called because the principal period of terrestrial nutation, driven by the same gravitational dynamics responsible for the precession of the lunar nodes, is approximated by the length of a Metonic cycle, a calculation device that helps keeping the calendar aligned closely with both the synodic month and the tropical year. In early Chinese calendars, the concept of refers to the length of one such cycle, namely 19 years. Despite this connection, the Earth's nutation is conceptually distinct from that of lunar procession, and in general the periods of nutation do not conform to simple multiples or fractions of calendrical periods.

The word appears to have been coined in the translation of 's Outlines of Astronomy into Chinese by and :

Noun

 * 1)  nutation