I raise this here instead of in a comment on the main site because the help page says, When shouldn't I comment: "Discussion of community behavior or site policies; please use meta instead."
Currently, there is no enw tag in existence (anymore?) and it's impossible to make a synonym on a nonexistent tag.
ENW - like other acronyms - should not be used as a tag, as it might mean multiple things, including 2 airstrips and a language. A synonym should be considered the moment it crops up next time.