lol, as far as my remembrance goes, I'm the one who created it! And, it was accidentally done!
When I joined this wonderful forum, I did not know that tags here don't have 'spaces' in between. Said that, if you have a question asking for some term, and you need to tag it, you type 'word-request' and NOT 'word + space + request'.
I know typing and my fingers work very very swiftly on keyboards. I think many questions I asked initially had to have 'word request' or 'word usage' but then since I type fast and there was 'no' space required, unbeknownst to me, 'word' is what ELL accepted. I might have removed the separated words 'request' or 'usage' then.
By the time I realized, the tag had become quite popular (many started using it, I mean). I then let it be there.
There's nothing wrong having this on board. If you think it's to be added to all those thousands of questions, I guess it goes true with other tags like 'grammar' as well! On this site, almost every question can be linked with 'grammar' one or the other way.
'Word' can be used for other reasons as well and not necessarily for 'word-usage/request'. What if someone wants to know 'word origin' or the difference between 'two words'? Even more... 'word type' (whether abusive, formal, informal). I can come up with a dozen more! :)