soap-bubble (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.

"small vesicle of water or some other fluid inflated with air or gas," early 14c., perhaps from Middle Dutch bobbel (n.) and/or Middle Low German bubbeln (v.), all probably of echoic origin. Figurative use in reference to anything wanting firmness, substance, or permanence is from 1590s. Specifically in reference to inflated markets or financial schemes originally in South Sea Bubble, which originated c. 1711 and collapsed 1720. Bubble-bath recorded by 1937. Bubble-shell is from 1847.