Here is something that I discovered at a very young age:
Pick any word, preferably a one syllable word. (Try using door, or the.)
Say it in the same tone for a while, and you’ll start questioning if it’s a real word or not. Maybe you’ll think the word just sounds strange, or that it should be called something else. Did you feel it?
i know what you’re talking about. i first realised that about names, and then with words in general. they’re just so funny! like a bunch of little funny social misfits.
I used to do it a lot in car rides! The, the, the, the, the , the, the , the… the the…
Try toe. That’s a good one.
The first word I did this with was “drawer”. 
Ive discovered that too, I think it was the swedish word: [spoiler]"Jag kom tyvärr inte på något 
"[/spoiler] It was not that sentence 
I always drop words when Im answering to threads like this 
I’ve noticed this with a lot of words, but most particularly spatula and whisk.
Why are so many cooking utensils named weirdly? I have no idea.
Heh yes this happens to me too.
“Earth” is one that got me.
Wow, so I’m not the only one doing this? But I never put an one syllabe word. It may be 2-letter as well as 12-letter (here 4,5 syllabes as usual). But I need to divide them first to make it easier.
I’ve often had this with other words… I used to think boy and girl both sounded silly, and the same for puddle. I never liked those words much.
“Tea, tea, tea, tea, tea, tea, tea…” 
I know, I get random moments where I think…toilet…it shouldn’t be a word…doesn’t sound like one!!
The swedish word “ej”, say it again and its not a word anymore, ej is swedish for not 
This phenomenon is actually called Jamais vu and doesnt have to be related to words only.