Hi Doug, the "Peral" was the electric submarine made by Isaac Peral in 1887 (https://en.wikipedia.org/wiki/Spanish_submarine_Peral). The surname "Peral" is, as you wrote, "pear tree" in Spanish. I used the historical origin of this engineer (Isaac Peral), who was birth in Cartagena, to write the background of the Brigade.
Cheers
*facepalm* I was vaguely aware of the submarine, but didn't connect to the name. Thanks for the EMBARRASSING clarification...
Doug