So, how is it that inner orange skin is called by a word...

Hey, are we still talking about the word zest here? Zest is the outer, most [orangest]orange[/orangest] part of the outer skin without any of the white [whitest]pith[/whitest] that is between the zest and the flesh of the orange. Or the same with a lime or lemon.

The zest is wonderfully edible in such things as "Orange Beef" or candied and used in recipes for "Chocolate Mousse". But the pith is very bitter and changes the flavor of the zest.

So, don't confuse the ZEST with the PITH!