By surface analysis, кипя́ (kipjá, “to boil, to seethe”) + -еж (-ež).
кипе́ж • (kipéž) m
- boiling, froth
- (figurative) ardour, impetus
- “кипеж”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Sofia: Bulgarian Academy of Sciences, 2014
- “кипеж”, in Речник на българския език [Dictionary of the Bulgarian Language] (in Bulgarian), Chitanka, 2010