unable to observe or perceive something directly before one or which is within one's powers of
observation or
perception. Literally, it means to be unable to see anything with the eyes or to have extremely poor vision. Although the
origin of this
phrase is unknown, it was first seen in the
late 1500s and is probably an allusion to the
bat, earlier
thought to be
blind or unable to see. The
bat is actually not "
blind," but relies on a
different method of "
sight" than the eyes. A
bat moves and flies by a
process, by which it sends out sounds (of a very
high tone that cannot be heard by the human
ear) which reflect off objects in the vicinity. The sounds bounce off the objects and by listening to the
returning echoes of the
sound, it can find the location of obstacles or prey.