If you want to code-switch so often that you are nearly incomprehensible to goyim, here is a list of my favorite and most-used Jewish terms:
Schvitzing - Sweating. (Ex: "I'm schvitzing so much it's showing through my clothes.")
Schlep - A tedious and long journey, depending on usage it can mean that you were carrying something. (Ex: "I had to schlep all the way across campus, my backpack was so heavy." Usually denotes a long walk, but other forms of transportation are acceptable too. "You drove all the way to New York from Florida? That's quite the shlep.")
Shtati - Something really cool. (Ex: "I visited my friend's place and they had a shtati mezuzah!")
Neshama - Soul. (Ex: "Mazel tov on your conversion, you have such a strong Jewish neshama!")
Balagan - A big mess, chaotic, confusing (Ex: "Moshe forgot to bring challah for shabbat dinner, and it turned into this big balagan")
Achi/Achoti - "Achi" literally means "my brother," but can also be used like bro or dude, "achoti" is the feminine equivalent meaning "sister"
Yalla - Come on, let's go (Ex: "Yalla yalla, you're going to make us late again")
Mishpacha - Family. Doesn't have to be literal blood relatives, usually a sign of warmth or friendship. (Ex: "I care about every Jew, they're all my mishpacha.")
Pshhh - Interjection sound, to express respect or agreement with what someone is saying, but can also be playfully poking fun at someone taking themselves too seriously, can be used sarcastically.
Achla - amazing, awesome, great, the best (Ex: "You graduated from university? Achla!")
Sheina Punem (Shayna Punim) - Pretty face (Ex: My bubbe kept pinching my cheeks and calling me a sheina punem) Can be used ironically, in which case it means "a disgrace."
Ahavat Yisrael - to love your fellow Jew (Ex: "I firmly believe in ahavat yisrael, even if it's hard sometimes.")
Schande - Shame, dishonor among the nations, meaning a Jew who represents Jews badly, a serious insult. (Ex: "He's a schande, he feeds into antisemitic stereotypes.")
Schmutz - Dirt, stain. (Ex: "Use your napkin, you've got schmutz on your face.")
Amalek - Any enemy of the Jewish people. ("[Fill in blank] is the modern Amalek, they hate the Jews.")
Lanceman/Landsmen - Two jews from the same place, a point of connection between two Jews who now live far away from their hometown. (Ex: "Your grandma is from Crown Heights? Mine too, our grandparents are landsmen!")
Goyisch - Something not Jewish (Ex: "I don't listen to Taylor Swift, her music is too goyisch for me.")
Goyischekop/Goyische-kop - Goyisch head, a jew who thinks/sounds like a non-jew. (Ex: "How could you say about your fellow Jew? Do you have a goyische-kop or something?")
Kindaleh/Kinderlach - Little children (Ex: "I passed by the school and saw the kindaleh on the playground, they're so cute!")
Chamud/Chamuda/Chamudi - Sweetie, cutie, usually aimed at children, but can be a term of endearment between a couple. Can be condescending when said rudely to another adult, like "Sweetheart" can be in English. (ex: "Goodnight, Chamudi. I can't wait to see you tomorrow.")
Daven - to pray ("Are you going to join us for davening?")
Frum - A religiously observant Jew. ("He's frum, he davens three times a day.")
Treif - Unkosher, generally something not good, doesn't have to literally refer to a food. ("I trained my dog to stop barking when I say 'treif!'.")
Bubkis - Zero, nothing, nada ("Moshe got a gift from bubbe and I got bubkis.")
Kvetch - To complain ("I'm just kvetching, I'm not that upset about it.")
Kvell - Extreme pride. ("I heard your daughter made it into her top school, you must be kvelling!")
Mensch - A good, admirable person. ("He volunteers every week, he's a mensch.")
Chillul HaShem - Disgracing God's name, someone who does something that makes Jews look bad.
Kiddush HaShem - Something that sanctifies God's name, brings honor to God. ("I love seeing you wear a kippah, it's a kiddush HaShem!")
Bubbe meise - Little white lies ("He told his teacher a bubbe meise about his dog eating his homework.")
I should acknowledge that these are mostly Yiddish words, as my experience is primarily with Ashkenazi Jews. If you would like to add common slang from your community (like Ladino phrases, Judeo-Arabic, Italki, etc) I would love to learn about them!
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