soap (n.) Look up soap at Dictionary.com
Old English sape "soap, salve" (originally a reddish hair dye used by Germanic warriors to give a frightening appearance), from Proto-Germanic *saipon "dripping thing, resin" (cognates: 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" (cognates: Latin sebum "tallow, suet, grease").

Romans and Greeks used oil to clean skin; the Romance language words for "soap" (cognates: 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 meaning "flattery" is recorded from 1853.
soap (v.) Look up soap at Dictionary.com
1580s, from soap (n.). Related: Soaped; soaping.