adjective/ˈfereo/
iron; persistent, determined, tenacious; powerful, hard; from the Iron Age
“idea férrea” — a tenacious idea
Etymology tree substratebor. Old Latin *fersom Latin ferrum Proto-Indo-European *-yósder. Proto-Indo-European *-éyos Proto-Italic *-ejos Proto-Italic *-eos Latin -eus Latin ferreusbor. Spanish férreo Borrowed from Latin ferreus (“made of iron; hard; rigid”).