Why did Bubby, grandma, always say that? And does it really have to do with the evil eye? Is this evil eye a cousin of walking under ladders with black cats on the Friday the thirteenth? The answers, in order, are: Because she loved you. Yes, but with an explanation. No.
Kenahora, although everyone thinks is a Yiddish word is actually three words slurred together in Yinglish –- the vibrant language of Native Americans of the Lower East Side: kein, the Yiddish word for no or negating, ayin Hebrew for eye, and hara, Hebrew for Evil.
Now think back to when she used it: "Such a sheine punim, kenahora." "You've grown, kenahora." "He's making money hand over fist, kenahora." (you should only be so lucky)
I have a friend in, well, I'm not saying where they're from, because I want to protect myself from what will happen if I don't protect their anonymity. They make in the seven-digits a year (kenahora). They drive a five-year-old station wagon. He once told me why she insisted on it. Their neighbors don't have as much, and their neighbors' neighbors have even less (and they're still not slumming, mind you). If she gets a new car then her neighbor will be compelled to keep up -- and her neighbor likewise. Somewhere down the line someone is going to be hurting from racing too hard. She doesn't want that frustration to be caused by her. And not for purely altruistic reasons.
G‑d gives us things. G‑d does not give others these same things. This can and does cause jealousy, an unvoiced "Why does she deserve it?" and somewhere on High that energy does not dissipate. It gravitates, and brings into question "Maybe she doesn't deserve it after all?"
Those-who-have-don't-show doesn't have to be grounded in smugness. We don't want that our good fortune should accentuate what others are missing. Which is why boasting is unJewish. And why when something said could be seen as boasting, it is hurriedly whispered and sandwiched between kenahoras and pu-pu-pu's.
The pu-pu-pu, incidentally, is spitting noises. Spitting as if in disgust. It's an appropriate Yiddishism: when you see an exceptionally beautiful child you say "Miyuskeit! Pu!" ("Disgusting!")
Asking Jewish grandmothers how many grandchildren they have can risk a faux pas. While some won't hesitate to blurt out a number, others will fidget and mumble. Putting a number on a blessing is considered bad taste.
You might also notice when they are counting a Minyan they won't count one-two-three but do something more convoluted.
Think it originated in Eastern Europe? This week's Parshah begins with the warning not to count people directly. (There is another reason not to count directly; it negates the quality of Infinite in the person, but that's for another time.)
See how much your Bubby loved you?