AudioBanter.com - View Single Post - What Does "XLR" Mean? -- Official Answer

Mike Rivers wrote:

In article writes:

As far as I know the XLR is just a series part number, it may have had an
original meaning, however we have no info here on it.

That seems to be as good an answer as any. There apparently was an XL
series of connector that was the same size and layout, but with a hard
insert. The XLR had a somewhat flexible rubber base for the insert,
and that's where the "R" came from (according to other folklore,
sometimes traceable to ITT Cannon).

I even have at least one old XL connector. Yup, hard plastic insert.

Cable gland is screwed on.

R for rubber sounds plausible.

Graham