People describe certain terms as a portmanteau of two other words, e.g. "fediverse is a portmanteau of federation and universe".
Unsurprisingly, portmanteau is itself a portmanteau, combining port and mantel, from Victorian south London where working men would exhibit their wealth by keeping a bottle of the best port they could afford on the shelf above the fireplace.
The Cockney pronunciation stuck, and was assumed to be of French extraction by typesetters.
