Why did Elly Koss need to take Acetaminophen?
why need to take Acetaminophen refers to REASONDESCRIPTION  where DESCRIPTION like 'Acetaminophen%' from medications;
SELECT T2.REASONDESCRIPTION FROM patients AS T1 INNER JOIN medications AS T2 ON T1.patient = T2.PATIENT WHERE T1.first = 'Elly' AND T1.last = 'Koss' AND T2.description LIKE 'Acetaminophen%'