I&#x27;m fairly sure it&#x27;s <i>never</i> been called Aqua; &quot;Aqua&quot; is the name of the standard UI look (cf. the NSAppearance class). But the window manager is Quartz: &quot;Quartz Compositor is the display server (and at the same time the compositing window manager) in OS X.&quot;<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Quartz_Compositor" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Quartz_Compositor</a><p>(Hence the name &quot;XQuartz&quot; for the X11 display server.)