Fumigation in modern common practice is about pesticide removal, but the historical use of the word was something closer to purification by smoke or of making aromatic smoke for medical treatment or as an offering in a spiritual context. From the Latin fumigare “to smoke”, noun. fumus “smoke, fumes”
The ancient use of the word is not so far removed as the modern usage as it may seem at first glance. The removal of vermin was often an important part of curing and preventing disease and purifying an area in a time when sanitation was not as great as it is today.