“Löjl” is such a weird backformed noun in Swedish. There once was a noun called “löje”, which meant ridicule in both senses but mostly the amusing sense. Then, the adjectival form of that, “löjlig”, still meant silly on both senses but more the disparaging sense. “Ridiculous!”
“Löje” is a bit archaic (outside of several fossilizing specific expressions that are still in use, like “göra till åtlöje”). When wanting to use a noun form of “löjlig”, instead of repurposing “löje”, which doesn’t have the same disparaging weight, people went two directions.
One is “löjligheter”. “Vad är det här för löjligheter?” a rich CEO might exclaim.
The other is “löjl”, which is more slangy, more something Buffy or Willow would say, “Vad är det här för löjl?”
Both mean “What ridiculousness is this?” (Or, in gloss order thanks to v2 rule: “vad (what) är (is) det här (this) för (for) löjl (ridiculousness)”)
Class differences aside, saying “löjligheter” over “löjl” isn’t more etymologically “correct”. The historic noun form is “löje”. Adding “-ig” and then “-heter” is no more lingustically sound than backforming a noun from an adjective via truncation.
Arguably English has the exact same journey: “ridicule” → “ridiculous” → “ridiculousness”. Arguably an even longer journey since you started with “rīdēre”, which means to laugh, so you have one extra step tacked on before everything.
So I don’t mean to slag your language. Only defending “löjl” here, in Swedish. Not trying to introduce “rid” or bring back the fad of saying “ridic” or in any other way police English.
Except one thing. The other day I saw an English-language post where someone called Sweden “Sverige”. That’s wrong. That’s the name for it in Swedish, not in English. And in Castellan it’s Suecia, Catalan it’s Suècia, and Portuguese it’s Suécia. We want the name of the country to be translated. Calling it “Sweden” in English is not offensive to us. Calling it “Sverige” as a one-off gag is completely fine but this was a serious context so it was in bad taste. Although my anti-nationalist streak was fascinated and kind of wished the poster had come up with an even more disparaging name for it like “Svedala”.