Is it ensure, insure, or assure?
1650s, from Latin olfactorius, from olfact-, past participle stem of olfacere "to get the smell of, sniff," from olere "emit a smell, give off a smell of" (see odor) + facere "make" (see factitious).
olfactory ol·fac·to·ry (ŏl-fāk'tə-rē, -trē, ōl-)adj. Of, relating to, or contributing to the sense of smell.
A descriptive term for the sense of smell.