The story
From old timer + -’s + disease, from the fact that the disease disproportionately affects older people, and because of the phonetic similarity between Alzheimer’s and old timer’s.
Etymology from Wiktionary, CC BY-SA 4.0.
old timer's disease
old tim·er's dis·easeToday it means: Eggcorn of Alzheimer's disease (“a disorder involving loss of mental functions resulting from brain tissue changes”). Full definition →