It's a play on bang, not bing. DuckDuckGo popularized searches with a bang ("!"), so that from the DDG page you could do a search on Wikipedia for example, without navigating to Wikipedia first and searching there. Other search engines use it too, like Kagi for example.

https://en.wikipedia.org/wiki/DuckDuckGo#Bangs

https://duckduckgo.com/bangs

https://help.kagi.com/kagi/features/bangs.html