It's the word 撚 which means penis (lan2 which sounds more like "lun"). You can pretty much stick it between many words, much like "fucking" in English, to add emphasis.

I don't know for sure how accurate this is, but I'm guessing it's the first entry in this Wiktionary definition: https://en.wiktionary.org/wiki/L#Chinese.

Can corroborate the previous replies; or taking the initials of the words like `sls` is common these days