I believe it's neither:
"The origin of queueing theory dates back to 1909, when Agner Krarup Erlang (1878–1929) published his fundamental paper on congestion in telephone traffic [for a brief account, see Saaty (1957), and for details on his life and work, see Brockmeyer et al. (1948)]." -- https://www.sciencedirect.com/topics/engineering/queueing-th...
In the early days of telephony, system load was measured by how much current was being drawn from the talk power supply. This was done with a watt-hour meter, calibrated in erlangs.[1]
(It's amazing how little logging went on in the phone system before computerized switching. But that's another subject.)
[1] https://physicsmuseum.uq.edu.au/erlangmeter
also the namesake of the unit fwiw