Can anyone explain what the etymology of "had better" is?
Once I read that "a survival of the subjunctive form had appears in constructions like had better and had best, as in We had better leave now. This use of had goes back to Middle English and is perfectly acceptable."
This page suggests it's a relatively modern form, not Old English, though I assume it could be Middle English: http://www.etymonline.com/index.php?...earchmode=none (scroll down a bit)
It is perfectly acceptable, and you do here 'we had best be leaving' as well. The form does suggest that it is a subjunctive.