The Short Version
Authoritative genetic databases and public-health agencies document that the symbol “MTHFR” comes from the enzyme’s chemical name, methylenetetrahydrofolate reductase. Sources that link the letters to a profanity describe it as a later pop-culture nickname based on sound similarity, not as the origin of the gene’s official name. No evidence shows the acronym was ever intended or derived from the phrase “motherf*ckr.”