In message , N_Cook
writes
Another sideways input from an ex-polar researcher
snip
Polar lows were (I think) unknown until satellite imagery showed their
existence. Prior to that, ones which came south (rather than forming
and decaying in the Iceland/Faeroes region) would probably have been
classed as secondary lows, i.e. developing further South rather than in
the area where they originally developed.

I don't think that's true. Gordon Manley in his "Climate and the British
Scene", which pre-dates satellite imagery, I think uses the term "polar
low" and he describes them pretty well.
--
John Hall
"Honest criticism is hard to take,
particularly from a relative, a friend,
an acquaintance, or a stranger." Franklin P Jones