The Hamlet Project

Keen, like, keen to dally as those puppets do?
Keen, like, smart, like quick, like, sharp like a knife?
Keen, like, eager and enthusiastic about the theatre?
Keen would seem to have started with knives – with sharpness – and metaphorically went to sharpness of sight. (Let not my keen eye see not the wound it makes…)
And keen just grew and expanded as a word and a concept. And yet now, I don’t think I’ve ever heard keen used to describe a blade, except in Shakespeare and other texts from centuries past.
Language winds around like a country road. It is not sharp or direct like a knife. Language development isn’t keen, is it?