sieve n.

Middle English sope, from Old English sape "soap, salve," anciently a reddish hair dye used by Germanic warriors to give a frightening appearance, from Proto-Germanic *saipon "dripping thing, resin" (source also of Middle Low German sepe, West Frisian sjippe, Dutch zeep, Old High German seiffa, German seife "soap," Old High German seifar "foam," Old English sipian "to drip"), from PIE *soi-bon-, from root *seib- "to pour out, drip, trickle" (perhaps also the source also of Latin sebum "tallow, suet, grease").

Romans and Greeks used oil to cleanse the skin; the Romance words for "soap" (Italian sapone, French savon, Spanish jabon) are from Late Latin sapo "pomade for coloring the hair" (first mentioned in Pliny), which is a Germanic loan-word, as is Finnish saippua. The figurative meaning "flattery" is recorded from 1853.

Middle English siften, from Old English siftan "pass or scatter (the finer parts of something) through a sieve," from Proto-Germanic *sib- (source also of Dutch ziften, Middle Low German sichten, German sichten "to sift;" see sieve (n.)).

The intransitive sense of "pass loosely or fall scatteredly" (of snow, light, etc.) is from 1590s, as is the meaning "clear or cleanse of impurities." The figurative or metaphoric sense of "look carefully through" is recorded by 1530s. Related: Sifted; sifting.