English retains an interesting variability in its indefinite article: "a pear" but "an apple." We used to have this -n form for possessives too, as in "Mine eyes have seen the glory…" But now we have no trouble saying "My eyes," and judging from the speech of my children, I'm sorry to say that we may be losing our a/an distinction, too. To my bafflement and dismay, P and T don't seem to have an as part of their active vocabulary.
Be that as it may, even if we eventually lose our pre-vowel variant for our indefinite article, it will still have left us with a legacy in the form of some of our nouns. See, an article and its following noun are usually pronounced run together as if they were all one word, and sometimes hearers parse the article/noun combination incorrectly. This is called "juncture loss."
Imagine that I were enthusiastically discoursing upon grammar (That shouldn't be too hard to imagine) and I kept mentioning something that sounded like "anarticle." If you were not a grammar aficionado you might not be sure whether I was talking about "an article" or "a narticle." If enough people misinterpreted the placement of the N, it could get attached to the wrong word and ultimately stick. This is called "metanalysis." (Remember that with Ns ending possessives, too, it would have been much rarer to hear the word in an unambiguous context. Keep in mind also that people spelled as they spoke, so there was no standardization in texts to reinforce the correct placement of the N.)
Here are some English words that have been struck by the Curse of the Wandering N. First, those that lost their N to the neighboring indefinite article:
adder was originally nadder, cognate with natrix, the Latin name for water snakes.
apron was originally napron, related to "napkin" and "napery."
umpire was originally noumpere, from French nonper, meaning one not equal.
orange came into English from the Spanish naranja, and misplaced its N on the way.
The N can wander the other direction, too. Here are a couple of words that gained their Ns from hanging out so often beside them.
I'll start with uncle, which was for a time interchangeable with nuncle, and shows up that way in Shakespeare about 10% of the time when brothers of parents are under discussion. However, the nuncle form has not stuck after all, so it doesn't fully count here.
nickname was originally ekename, meaning "extra name."
newt was originally ewte, and it's just a fabulous word either with the N or without.
[Picture: Newt, wood block print with multiple blocks by C.B. Falls, from ABC Book, 1923;
Newt Poster, linoleum block print with multiple blocks by Christopher Wormell for California Coastal Cleanup Day, 2004.]