sniff (v.) Look up sniff at
mid-14c., of imitative origin; possibly related to snyvelen (see snivel). As an expression of scorn or contempt from 1729. As a synonym for smell (v.) it dates from 1845. In reference to cocaine from 1925. Related: Sniffed; sniffing.
sniff (n.) Look up sniff at
1767, from sniff (v.); the scornful sense is from 1859.