mercurial

The story

1. Latin · derived frommercuriālis“a plant, probably annual mercury (Mercurialis annua)”
2. Old French · derived frommercurial
3. Anglo-Norman · derived frommercurial
4. Middle English · inherited frommercurial“a plant, probably the goosefoot (Chenopodium); (possibly) dog’s mercury (Mercurialis perennis)”
5. English todaymercurial

Noun sense 1 (“(obsolete) plant known as mercury”) is from Middle English mercurial (“a plant, probably the goosefoot (Chenopodium); (possibly) dog’s mercury (Mercurialis perennis)”), from Anglo-Norman mercurial, Old French mercurial, or directly from their etymon Latin mercuriālis (“a plant, probably annual mercury (Mercurialis annua)”), short for herba mercuriālis (“(probably) annual mercury”, literally “herb or plant of the god Mercury”). Mercuriālis (“pertaining to the Roman god Mercury”, adjective) is derived from Mercurius (“the Roman god Mercury”) + -ālis (suffix forming adjectives of relationship from nouns). Later adjective and noun uses may have been directly derived from Latin mercuriālis (adjective), whence Middle English mercurial (“under the astrological influence of the planet Mercury”).

Words from the same roots

First known use, by meaning

• 13th–17th c. Any of the plants known as mercury, especially the annual mercury or French mercury (Mercurialis annua).
• from 16th c. A person born under the influence of the planet Mercury; hence, a person having an eloquent, quickwitted, furtive, or volatile character.
• from 17th c. A preparation of mercury, especially as a treatment for syphilis.
• from 17th c. Having a lively or volatile character; animated, changeable, quick-witted.
• from 16th c. Pertaining to the astrological influence of the planet Mercury; having the characteristics of a person under such influence (see adjective sense 1).
• from 16th c., from 14th c. Middle English Pertaining to the planet Mercury.
• from 16th c. Of or pertaining to the element mercury or quicksilver; containing mercury.
• from 15th c. Pertaining to Mercury, the Roman god of, among other things, commerce, financial gain, communication, and thieves and trickery; hence (comparable), money-making; crafty.