Twenty years ago Fowler pointed out that this word was having "very curious experiences" in that, although an adverb, it was being used more and more both as an adjective and as a noun. These experiences have certainly not abated since then.
The adjective that otherwise dispossesses is other. This is exemplified in such a sentence as "There are many difficulties, legal and otherwise, about doing what you ask".
The noun that otherwise dispossesses is whatever noun has the contrary meaning to one just mentioned. This is exemplified in such a sentence as "I will say nothing about the reasonableness or otherwise of what you ask", where the word replaced is unreasonableness.
Fowler condemns both these as ungrammatical. Since it is just as easy in the first case to write other and in the second either to omit or otherwise or to substitute the appropriate noun, there is no reason why one should not be on the safe side and do the grammatical thing. But it would be wrong to leave the subject without quoting Dr. Ballard:
A new pronoun is as rare a phenomenon as a new comet. Yet it dawned on me the other day that a new pronoun had insidiously crept into the English language. It was heard on everybody's lips, it was used on the platform and in the Press, it figured prominently in blue-books and official papers. And yet I could find it in no dictionary — not, that is, as a pronoun — nor could I discover it among the lists of pronouns in any grammar, however modern. Still, if the current definition is correct, the word is beyond doubt a pronoun. The word is otherwise. A committee is appointed by an educational body to report on the success or otherwise of the new organisation of schools. What does otherwise stand for? Why failure, of course. And failure is a noun. Therefore otherwise is a pronoun. . .I thought at first with Mr. H. W. Fowler that otherwise, so used, was not a pronoun but a blunder. But when I considered the people who used it so — schoolmasters and school inspectors, and ambassadors, and statesmen and judges on the bench — I could not accept Mr. Fowler's views. For I would rather wrong the dead — dead languages that is — and wrong myself and you than I would wrong such honourable men. There is no help for it. Otherwise is a pronoun.
Sometimes other gets its revenge, and supplants otherwise.
It is news to me that a sheep improves the land other than by the food fed through it.