From Wiktionary, the free dictionary
From কিয় (kiô) + বা (ba).
কিয়বা • (kiba)
- why? (used when the asker doesn't expect the answer from the person the asker is asking):
A: ঐ, আজি চাৰৰ আমাৰ ওপৰত খং উঠিছে যেন লাগিছে!
B: অ! কিয়݁বা!- A: oi, azi saror amar üporot khoṅ uthise zen lagise!
B: o! kioba! - A: Hey, it seems today the teacher is angry at us!
B: Yeah! why!