Connector-- vocabulary breakdown.

[no_one]

to keep you from getting electrocuted if you connect the one end to the
circuit and forget to put the other end into the meter.

 

[Michael A. Terrell]

They're called "phone jacks", because, historically, headphones used a pair
of tips that size. Nowdays of course we use a 1/4" TRS jack for that
purpose, but the name stuck.

I always saw them referred to as "Phone tip plugs" and jacks.

 

[Paul Hovnanian P.E.]

to keep you from getting electrocuted if you connect the one end to the
circuit and forget to put the other end into the meter.

Yep. I believe the part inside the shroud is still a banana plug. You
can still plug an unsheathed banana plug into the jack compatible with
these.