Nani is Japanese for "What" and is used in english sometimes as a dank comeback for when someone says something wired, stupid or just uncomfortable to thing of.
"i have 17 Mongolian children locked up in my basement" Response: "NANI?????"
"ç§ã¯ããªããæã£ã¦ãã¾ãç§ã¯æã£ã¦ãã¾ãã" Response: "Nani?"