"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.
late 15c., bobelen, "to form or rise in bubbles," perhaps from bubble (n.) and/or from Middle Low German bubbeln (v.), which is probably of echoic origin. From 1610s as "cause to bubble." Related: Bubbled; bubbling.