How do I get rid of "movies" taking up so much space?
Firstly - do not worry about "Other". This is a catch-all category and will include lots of system-only files, uncategorizable files etc. Unless these are stored within your user home directories then don't worry about them.

According to OSX Daily, the summary overview in Disk Utility will give a total for all video files - anywhere on the disk. Some of these may be in iTunes locations (including podcasts and iTunes U). A small few will be videos within system locations such as /System/Library/Compositions. You may find that a large number are part of your installed applications and their support libraries (this will depend on which applications you have installed, of course).

One way of searching for these video files is to use the Finder search box and type 'movie', then select 'kind = movie' from the system suggestions dropdown. Make sure that you select 'This Mac' for your search scope, and you should see all the files and their locations. There are lots of disk usage-reporting apps available to make this process simpler. 


Don't delete any files within /System or /Library. 
Don't delete any
files within /Applications or /Library/Application Support unless you
accept the risk of breaking those apps and reinstalling them.