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Porn is recognized by the iPhone & iTunes as "other". :apple:

You need to delete all those dirty vids.
 
Anything you may have uploaded to apps via their own folders.

I have tons of comic books and movies loaded into a few apps, on my iPad, and they all show up as "other".
 
their is a similar discussion on the iPad forum with many members asking the same question, and some members report to having up-to 6 gb of other.

https://forums.macrumors.com/threads/1081908/

I myself am having the same issue on my iPad and iPhone and i can't seem to pin-point the issue. I have gone as far as to taking my iPad in to the Genius Bar, they have no fix and say its an OS problem.
 
I have this problem, I've found it's music/videos that you have removed from your phone, where the file is removed from the library, but not from the phone.

the only fix I've found so far, is to turn off music/podcast/film/tv show etc syncing. Sync to remove all your media.
then download and run iPhone explorer (does not require jailbreak), go to the media/itunes folder and delete the mp3's/video's (which shouldn't be there as you just un-sync'd them!) While doing this you'll see "other" shrink in iTunes, down to about 0.4 gig.
repeat every month or so, hope they fix this bug soon!

(it's not files sync'd to applications like VLC, that all goes under "apps)
 
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