In the second episode of Watashi no Shiawase na Kekkon, one of the characters has two daughters: one natural that can see supernatural things, and a stepdaughter (which she bullies) that can't; about them, she says this:
いつまで経っても見鬼のけの字も現れない穀潰しとは大違いね
見鬼 is the ability to see the supernatural, and the sentence means something like "She is very different from a useless daughter which no matter how much time passes can't see the supernatural", but I can't understand けの字. I tried looking on Google an on dictionary, but nothing came up.