adverb, adverb taking the 'to' particle
complaining; nitpicking
Used for grumbling or finding fault, often with a negative nuance. Commonly appears with 言う or 文句を言う.
彼はいつもつべこべ文句を言っている。
He is always complaining about something.
つべこべ言わずに、さっさと仕事をしなさい。
Stop nitpicking and get on with your work.
Mimetic word; the exact origin is uncertain, but it likely imitates the sound of grumbling or chattering.