the.com/millwheel

means A large wheel turned by flowing or falling water, used to power a mill for grinding grain or driving machinery.

from A straightforward compound of 'mill' (from Latin 'mola,' meaning millstone, via Old English 'myln') and 'wheel' (from Old English 'hweol,' tracing back to a very old Indo-European root for turning or rolling — the same root that gives us 'cycle'). No hidden story here: the word simply names the thing, a wheel built to run a mill, and has worked that plain job since medieval times.