Jerusalem artichokes are neither artichokes nor from Jerusalem.  It seems their name is a corruption of ‘girasole’, Italian for sunflower, as the plant is indeed a relative, complete with bright yellow flowers and head-turning properties.  They originated in North America and first arrived in the UK in 1617, via France.  Their flavour is distinctly artichokey, which probably explains the first half of their name.  In the United States now they’re called ‘sunchokes’, which, as much as I hate invented conjoined abbreviations, is probably a more sensible name.