You Say "Potato" and I Say... "LATKES"!!
The award for the stupidest word in the English language officially goes to "phylacteries". What the hell are phylacteries? Well, according to the Oxford American Dictionary, they are "small leather box[es] containing Hebrew texts on vellum, worn by Jewish men at morning prayer as a reminder to keep the law". Ohh, Tefillin ! Why didn't you say so? You see "phylactery" comes from Greek (φυλακτηριον) and literally means an 'amulet'. Only it is never used to refer to an amulet, you see: it only ever means Tefillin. So if we expect non-Jews to learn the word "phylactery", why can't they just learn to use the word Tefillin instead??
Philologos has a great article in The Forward that touches upon just this issue.