My niece started saying 'Huh' way before she picked useful words in any language. Although she's been living in a multilingual environment, 'Huh' seems to be a built-in. Maybe it's just a grunt sound, maybe an actual word.
Ref:
[1] My niece says 'Huh' to signal confusion - https://www.youtube.com/watch?v=Sq_xxtZ76aI
[2] Huh? Is That a Universal Word? - https://www.americanscientist.org/article/huh-is-that-a-universal-word
