NLS Revert
Yes, your revert is in error. NLS is the origination of 'on-line'. Why don't you actually compare the meaning of the word with the Wikipedia article I provided? Douglas Engelbart and his NLS project introduced the word 'on-line'. It was meant to distinguish between interaction with mainframe computers which required punch-cards to program -- these, Doug referred to as off-line systems -- rather than a console, or even an "on-line system", which is the concept he defined and pioneered with NLS.
Note: If you're more familiar with the modern "connected to the Internet/network" meaning of the word, you should know that both NLS and ARPANET were developed at SRI. The term came from NLS.
The origin of the term has nothing to do with it. "See" followed by a link to Wikipedia isn't a definition, and so doesn't belong where you put it. A succinct explanation of the origin of the term can go under an Etymology header, and the "See" bit can go under an External links header (though there are better ways to format it than a full url). See WT:ELE for information on our rather extensive and specific formatting requirements so you won't unintentionally trash any more entries. I should add that the additions I mentioned should go at the main entry, online, not at on-line, which is supposed to merely refer to the main entry (to have content at both makes it hard to keep them in synch).