The story
Initialism. The TO originally stood for "toxoplasmosis" but is now understood as "toxoplasmosis and other infections".
Etymology from Wiktionary, CC BY-SA 4.0.
TORCH complex
Today it means: A set of perinatal infections that can lead to anomalies or fetal loss: toxoplasmosis, other infections, rubella, cytomegalovirus, and herpes simplex virus-2. Full definition →