"Odor source" refers to something that is causing a particular smell or aroma. It is the origin or location from which the odor is originating. Full definition
Daisuke Kurabayashi, Yosuke Takahashi, Ryo Minegishi, Elisa Tosello, Enrico Pagello, Ryohei Kanzaki Modification in Command Neural Signals of an Insect's Odor Source Searching Behavior on the Brain - Machine Hybrid System. (csnetwork.eu)
Major process odor sources include singeing, scalding, lairage, wastewater treatment and rendering. (cstwastewater.com)
By genetic manipulation, Bargmann and her team swapped the receptors for two different odorants between two neurons, and produced opposite effects to those that normally occur — a receptor for an attractive odor, now on a neuron that usually responded to noxious odors, caused worms to move away from the attractive odor source. (kavliprize.org)