The Wrong Word Syndrome

I was talking to my friend on the phone the other day, and he proceeded to explain to me that his friend was using a foil to hide his true feelings. I inquired of him, what does using a foil mean? He then quizzically asked me, isn't that a literary term? Shouldn't you know that as an English major? In fact, I do know what a foil is, I was simply trying to figure out if how he was using it made any sense. And it doesn't.

I have another friend, who whenever she is feeling sick explains that she is ill-faded. I have never heard that term before, but believe she is confusing it with the phrase "ill fated," which possibly makes even less sense than the initial mangled phrase.

Still, I overhear conversations and hear people just butcher words, replacing words that sound similar for unknown reasons. For example, consider the following exchange:
"Man, you should have been there last night."
"Really, was it that good?"
"Yeah, I mean the party was awesome, it was incredulous."

Here, the user is clearly meaning to use the term to be incredible. And that is a completely legitimate use. According to Merriam-Webster (the dictionary for people who like first names), incredible is the second definition for incredulous. Yet, I'm guessing the speaker was trying to use it as "extraordinary" or "amazing" not simply something that he did not believe, as incredulous is traditionally used. I suppose, the fact that incredible can mean "extraordinary" or "amazing" gives credence to the fact that the meanings of words change, but in context, the sentence just sounds goofy. I always imagine a precocious fifth grader trying to drop in a new vocab word just to see what happens. What happens is that people listening absorb the word, and copy its usage in new conversations. My friend with the "foil" usage later confided that he heard the word used earlier in the week tried to guess its meaning, and implement it accordingly.

The ironic thing is, I'm guessing this is how we have acquired language since we were young. You heard a word, guessed its usage, and tried it out to get peoples reactions. This is also why the meaning of words consistently change. Maybe its old school, but words used in awkward ways still grate on my ears. I feel as if I hear these misplaced words dropped all the time (and admittedly, I'm more than sure I do it myself), but in writing this, I can hardly think of any examples. Maybe its just a defense mechanism of my mind to keep myself from exclaiming that when something terrible happens, it was "terrigenous."