One of the mysteries of the English language finally explained.
Definition of planetic in English:
planetic
adjective
1Astronomy and Astrology. Of, relating to, or caused by a planet or planets; = "planetary" 1b. Now rare.
2Biology. Of, relating to, or designating a dispersal stage in certain fungi and algae, involving motile cells or spores or (in later use) the transfer of nuclei between cells.
Origin
Mid 17th century. From post-classical Latin planeticus wandering from Hellenistic Greek πλανητικός wandering, of or relating to a planet from ancient Greek πλανητός wandering, used occasionally of planets + -ικός. Compare French † planetique.