The term agnosia was first introduced in 1891 by Sigmund Freud, and generally refers to an acquired loss of recognition, where although a given sensory modality appears to be intact, the ability to recognize an object, person or other specific entity is no longer present.
Freud, Sigmund (1891). Zur Auffassung Der Aphasien: Eine Kritische Studie. Franz Deuticke: Wien & Leipzig. 80
Benson, D.F. & Ardila, A. (1996). Aphasia: A Clinical Perspective. New York: Oxford University Press. 303