Merriam-Webster's Collegiate® Dictionary, 11th Edition
CHURN
I. noun
Etymology: Middle English chyrne, from Old English cyrin; akin to Old Norse kjarni churn Date: before 12th century a vessel for making butter in which milk or cream is agitated in order to separate the oily globules from the watery medium,
II. verb
Date: 15th century
transitive verb to agitate (milk or cream) in a churn in order to make butter,
2. to stir or agitate violently , to make (as foam) by so doing, to make (the account of a client) excessively active by frequent purchases and sales primarily in order to generate commissions, intransitive verb to work a churn,
2. to produce, proceed with, or experience violent motion or agitation , to proceed by or as if by means of rotating members (as wheels or propellers)