Baru stems from an Irish vodka and it means to stretch the truth. It is pronounced like DA BEARS but its BA RU. It is used following a false or made up statement.
"En's buttocks are pretty barunga if you ask me"
"Who's that guy over there with the big barunga?" "Oh that's the famous Sicillian V-tuber, Enrico Zenitani"
Sometimes written as "Balse".
The nickname Ram calls Subaru in the anime Re:Zero kara Hajimeru Isekai Seikatsu ( AKA. Re: Life in a Different World from Zero). It is created by swapping the “su” to the end of "Subaru". Su baru > Baru su
The nickname is first used in Season 1 Episode 4. During the scene, Subaru is trying out new clothes for his job at Roswaal's Mansion.
Rem: Our deepest apologies, sir. I mean, Subaru-kun.
Ram: You look quite ridiculous, sir. I mean Barusu.
Subaru: Hey, Onesan, you just turned my name into a blinding curse.