Mercurialist
/məːˈkjʊərɪəlɪst/Now historical and rare
noun
A person born under the influence of the planet Mercury; a person having the qualities attributed to such a birth, especially eloquence, ingenuity, or aptitude for trade. Also occasionally with unfavourable connotation: a sharper, a thief.
Origin
Mid 16th century; earliest use found in Thomas Drant (c1540–1578), poet and Church of England clergyman. From mercurial + -ist.