late 14c., in reference to the fruit of the orange tree (late 13c. as a surname), from Old French orange, orenge (12c., Modern French orange), from Medieval Latin pomum de orenge, from Italian arancia, originally narancia (Venetian naranza), an alteration of Arabic naranj, from Persian narang, from Sanskrit naranga-s "orange tree," a word of uncertain origin.
Not used as a color word in English until 1510s (orange color), "a reddish-yellow color like that of a ripe orange." Colors similar to modern orange in Middle English might be called citrine or saffron. Loss of initial n- probably is due to confusion with the definite article (as in une narange, una narancia), but also perhaps was by influence of French or "gold." The name of the town of Orange in France (see Orangemen) perhaps was deformed by the name of the fruit. Orange juice is attested from 1723.
The tree's original range probably was northern India. The Persian orange, grown widely in southern Europe after its introduction in Italy 11c., was bitter; sweet oranges were brought to Europe 15c. from India by Portuguese traders and quickly displaced the bitter variety, but only Modern Greek still seems to distinguish the bitter (nerantzi) from the sweet (portokali "Portuguese") orange.
Portuguese, Spanish, Arab, and Dutch sailors planted citrus trees along trade routes to prevent scurvy. On his second voyage in 1493, Christopher Columbus brought the seeds of oranges, lemons and citrons to Haiti and the Caribbean. Introduced in Florida (along with lemons) in 1513 by Spanish explorer Juan Ponce de Leon. It was introduced to Hawaii in 1792.
Since Middle English restricted to use as the common name of the viper, the only poisonous British reptile (not generally fatal to humans), then by extension applied to venomous or similar snakes elsewhere (puff-adder, etc.). The modern form represents a faulty separation 14c.-16c. of a nadder into an adder, for which see also apron, auger, nickname, orange, humble pie, aitchbone, umpire. Nedder is still a northern English dialect form. Folklore connection with deafness is via Psalms lviii.1-5. The adder is said to stop up its ears to avoid hearing the snake charmer called in to drive it away.