'Other' refers to data that iTunes can't categorise - such as app data - e.g. map data etc. If you have a significant number of apps of this type, that could explain the 'Other' category.
There have been several reports from Members about 'spurious' 'Other' data and several have found that a 'Restore' cleared this up. One Member, just this morning, reported that his excessive 'Other' was reduced to nearly zero when he updated iOS. But, if you search on the net, you'll see excessive 'Other' is a common problem for which there appears to be no guaranteed solution.
Tim