From Middle High German dampf, tampf, from Old High German thamph, damph, tamph, from Proto-Germanic *dampaz. Given the predominant d- in Old High German and quite frequent attestations with th- in related words, the underlying form in High German is probably *þampaz; also attested in the Old Saxon verb thempian. The origin of this byform seems unclear. Eventually derived from Proto-Germanic *dimpaną (“to steam; vaporise”).
- “Dampf” in Duden online