pendulation
/pɛndjʊˈleɪʃn/ /pɛndʒʊˈleɪʃn/noun
1 Physical Geography. A supposed oscillatory motion of the earth's poles across its surface. Now rare.
2An oscillatory motion like that of a pendulum (literal and figurative ); an alternation between opposite positions.
Origin
Early 20th century; earliest use found in Science. Partly from pendulum + -ation, and partly from pendulate + -ion; compare -ation.