It's Not What I Mean (34 pics)

These are called Malapropisms, named after the pompous character Mrs. Malaprop, humorous aunt who gets mixed up in the schemes and dreams of young lovers in Richard Sheridan's 1775 play "The Rivals."
Some classic ones that have appeared in hospitals are:
“old timer’s disease,” “prostrate cancer,” “chickenpops,” “smiling mighty Jesus” (for spinal meningitis), and “65 roses” (for cystic fibrosis)