the less correct, but more popular, spelling of aneurysm (q.v.), by influence of words in -ism. The -y- is etymologically correct; the spelling with -i- suggests a meaning "nervelessness."
early 15c., from Medieval Latin aneurisma, from Greek aneurysmos "dilation," from aneurynein "to dilate," from ana- "up" (see ana-) + eurynein "widen," from eurys "broad, wide," from PIE root *were- "wide, broad" (cf. Sanskrit uruh "broad, wide").
A localized, blood-filled dilation of a blood vessel or cardiac chamber caused by disease, such as arteriosclerosis, or weakening of the vessel or chamber wall. A ruptured aneurysm results in hemorrhage and is often fatal.