Is it ensure, insure, or assure?
1819, frequentative form of sniff (v.). Related: Sniffled; sniffling. The sniffles "runny nose, head cold" is recorded from 1825. Sniffly (1897) tends to refer to physical symptoms, while sniffy (1858) means "scornful, disdainful and disagreeable." Snuffy "annoyed" is from 1670s.