Lest we forget:
orange - c.1380, from O.Fr. orenge, from M.L. pomum de
orenge, alt. of Ar. naranj, from Pers. narang, from Sansk.
naranga-s "orange tree." Loss of initial n- probably due to
confusion with definite article. Introduced in Florida (along with
lemons) 1513 by Sp. explorer Juan Ponce de Leon.
Introduced to Hawaii 1792. Not used as the name of a color
until 1542. Orangemen refers to Irish secret society founded
1795 in Belfast, named for William of Orange (who became
William III of England), of the Ger. House of Nassau; the
name from the town of Orange on the Rhone in France, which
was part of the principality, so called because it was said to
have been a center for importing oranges.

And:
Citrus is, in last consequence, derived from Greek
kedromÍlon "apple of cedar" (Greek mÍlon is cognate to
Latin malum "apple"); this name, however, did not signify
lemon, but citron (see above), whose cultivation in Egypt is reported by Greek travelers.
The Romans, then, shortened the Greek name to citrus.

For the botanical species name, limon, and the English name lemon, see lime.

The German formation Zitronatzitrone "citron", rather puzzling at first sight, is a simple
compound (primary word Zitrone "lemon", determinative element Zitronat "succade")
meaning "lemon whose peel is used for making succade".