Meaning

noun an arc of colored light in the sky caused by refraction of the sun's rays by rain

noun an illusory hope

originFrom Middle English reynbowe, raynbowe, from Old English reġnboga (“rainbow”), from Proto-West Germanic *regnabogō, from Proto-Germanic *regnabugô (“rainbow”), equivalent to rain + bow (“arch”). Cognate with West Frisian reinbôge (“rainbow”), Dutch regenboog (“rainbow”), German Regenbogen (“rainbow”), Danish regnbue (“rainbow”), Swedish regnbåge (“rainbow”), Icelandic regnbogi (“rainbow”).

Etymology from Wiktionary, CC BY-SA 3.0