Definition
Utterly and completely lost; lost in a remote location.
Origins
Possibly from Puhoi.
How People Actually Use It
Lost or awry. A remote, out of the way or non-existent place, far from civilisation. Possibly derived from the place-name Puhoi. Sometimes used to describe a person's confused state of mind. New Zealand rural slang.
""Where's Trevor?" "Up the boohai somewhere.""
Source: Urban Dictionary