Seen on a corporate flyer, this malaphor is a subtle congruent conflation of “over the edge” and “off the deep end”, both meaning to act irrationally or out of control. Both phrases describe a precipice, hence the confusion. Also the words “off” and “over” are similar in sound and shape. I think “edge” and “end” also contribute to the mental hiccup. A big thanks to Marcia Johnston, author of several books and the website writing.rocks, for spotting this one and passing it on!