archaism

noun

Etymology: 17th century, from New Latin archaismus, from Ancient Greek ἀρχαϊσμός (arkhaïsmós, “an antiquated phrase or style”), from ἀρχαίζω (arkhaízō, “to model one's style upon that of ancient writers”), from ἀρχαῖος (arkhaîos, “old, ancient”), from ἀρχή (arkhḗ, “beginning”), from ἄρχω (árkhō, “I begin”), from Proto-Indo-European *h₂ergʰ- (“to begin, rule, command”).

1. The adoption or imitation of archaic words or style.
2. An archaic word, style, etc.

   “In this text, the word "methinks" appears to be a deliberate archaism.”

   “He had the fastidiousness, the preciosity, the love of archaisms, of your true decadent.”