"sense of smell, faculty of smelling," 1846, noun of action from Latin olfactus, past participle of olfacere "to smell, get the smell of" (transitive), from olere "to emit a smell" (see odor) + facere "to make" (from PIE root *dhe- "to set, put").
oleander
Oleg
oleo
oleo-
oleomargarine
olfaction
olfactory
Olga
oligarch
oligarchic
oligarchy