Reg, G4FGQ wrote:
"Call out the riot police!"

And a riotous new year to you too!

An SWR meter is a built-in or external circuit which measures the
standing-wave-ratio at the transciever end of the feedline. Actually it
measures the degree of mismatch which causes SWR.

SWR = R/Zo or Zo/R, as required for a quotient1.

At the junction of a uniform feedline and a mismatched antenna load, the
reflection coefficient is a vector ratio between the electric fields
associated with the reflected and incident waves. The magnitude of Rho,
the reflection coefficient, is related to VSWR by:

Rho = VSWR - 1 / VSWR + 1

So, mismatch produces reflection, the magnitude of which depends on how
great the mismatch. The reflected wave traveling back toward the source
of the incident wave makes a standing-wave-pattern. SWR is the ratio of
the maximum of voltage (or current) along the line if the line is long
enough. If not, an SWR may be inferred from the forward and reflected
powers for practical purposes.

The built-in or external meter that indicates severity of mismatch, is
usually labeled "SWR" because the determination was traditionally made
by sensing the sum of forward and reverse fields, either electric or
magnetic, along the transmission line. The ratio of maximum to minimum
is SWR.

The meter could have been called a "mismatch meter", but that won`t
happen. "SWR meter" is ingrained.

"Water Tank" was a code name given the military vehicle by its British
developers during WW-1 to maintain secrecy. After they were fielded,
attempts were made to no avail to call the vehicles "assault carriages"
or "combat cars". "Tank" is the name now and forever. Same with "SWR
meter".

Best regards, Richard Harrison, KB5WZI