Definition of "yawny"

Waking up in the small room, you feel dull, stupid, gloomy, oppressed, yawny, lax, and all unstrung in body and mind...

1848, Orson Squire Fowler, A Home for All

I drew the deepest, yawniest breath I could fake and swiftly lifted my right arm.

2011, Craig Groeschel, Love, Sex, and Happily Ever After, page 13