Harry Bloomfield wrote:

Matthias Czech wrote:

Harry Bloomfield wrote:

What's the meaning of 'heavy', in United 328 heavy?

https://en.wikipedia.org/wiki/Heavy_(aeronautics)

which suggests...
Heavy (aeronautics), a term used by pilots and air traffic controllers
to refer to aircraft capable of 300,000 lbs or more takeoff weight

And therefore of interest to pilots of smaller planes following them, as
they create greater turbulence, so the callsign suffix makes it obvious.