The expression "bada bing" and often accompanied by "bada boom" is used when something was very easily accomplished or as an euphemism of the nastier bits of something (like in the Godfather). A quick look on Wiktionary and Urban Dictionary confirms this.
It seems onomatopoetic because of bing and boom, but where does the "bada" come from? The whole phrase seems to be a recent invention according to this Ngram, starting in the late 1980's (surprising it was not sooner with the popularity of the aforementioned Godfather being released in 1972) peaking in the 2000's (possibly in part to the popularity of The Soprano's). The phrase does seem to go hand in hand with Mafioso culture as well.
So, where does this phrase come from and when did it take on its current meaning?
Best Answer
The earliest usage of bada bing dates back to 1965, according to the Oxford English Dictionary and Merriam-Webster.
About its etymology, the OED says 'Origin uncertain. Perhaps imitative of the sound of a drum roll and cymbal clash (compare boom-boom int.)'. Lexico says it was popularised by the US TV series The Sopranos. Dictionary.com says 'perhaps imitative of the sound of something clicking into place'. However, the real origin is unknown as mentioned by the OED.
Here's the example from 1965, used by Pat Cooper:
According to WordSmith: