I don't think that it "slipped through". The term "lash up" is a hobbyist term, and you will even find the term in the likes of Trains Magazine! The hobbyists "understand" what Lionel, MTH, Atlas, Weaver, Athearn, etc. are explaining when they are putting together an MU'ed consist of diesel units. Making them all run together electronically under TMCC, DCS, and DCC has always been referred to as a "lash up". Many rail fans use it, but I have never understood where, when, or who ever came up with it. I would love to see the ropes that are used to "lash units together"!