A person who writes elegies; a poet specializing in elegiac verse or mournful poetry.
From elegy (Greek elegeia) plus the agent suffix -ist (meaning 'one who practices'). The -ist suffix is one of the most productive ways English creates nouns for people who do specific things.
An elegist was basically a specialist grief-writer in ancient times—the person you'd hire to write the official poem mourning a famous person, so they had to be really good at capturing sorrow beautifully.
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