Ruiner comes from ruin + -er, from Old French ruine, from Latin ruina ('a collapse'), from ruere ('to fall, rush down'). The historical chain includes Latin ruina and Latin ruere. Older glosses in the chain include "a collapse" and "to fall, rush down", which help explain the semantic range of the modern word. Morphologically, ruiner is best read as compound, suffixal formation, and borrowing, yielding an English noun shaped by both form history and later usage. In current English it functions as a noun, with the sense "a person or thing that ruins or destroys something". related forms include ruin, ruination, and ruinous. The result is an English noun whose etymology preserves the older forms while supporting the word's specialized modern meaning.