not for nothing

The construction predates the 20th century. Its use as a disjunct is common in the 21st century but was either rare or absent before that.

not for nothing

2. Not for no reason; not without reason; (often) for a good reason.

   Synonym: with good reason (often synonymous)

   Antonyms: for nothing, for no good reason

   Not for nothing did he wait until a moment when Mommy wasn't home to ask for Daddy's permission to watch an R-rated movie.

   • 1999, Suzanne Bakker, Libraries without Limits, →ISBN:

     Not for nothing is it called the World Wide Wait. Not for nothing has a Dilbert cartoon appeared noting that all the time saved through automation and computers in the last fifty years has been entirely outweighed by people sitting in front of pc's waiting for web pages to load.

   • 2006, Igor Mel'cuk, David Beck, Aspects of the Theory of Morphology, →ISBN, page 563:

     It is not for nothing that linguistics began with morphology and for a couple of centuries was practically nothing more than morphology.

   • 2012, Josephine Tey, A Shilling for Candles, →ISBN, page 96:

     But not for nothing had Hopkins trailed Grant from Wigmore Street to the Orient offices, and from the Orient offices to the Temple, and from the Temple to the Yard. Not for nothing had he cooled his heels round the corner while his paid henchman kept watch on the Yard and gave him the sign when Grant left. Not for nothing had he followed him all the way to Westover.

   • 2024 May 21, Joel Guinto, Simon Fraser, quoting John Strickland, “One dead as London-Singapore flight hit by turbulence”, in BBC News‎:

     "It is not for nothing that airlines recommend keeping seat belts loosely fastened throughout a flight be it long or short," he added.

4. (as a disjunct) Used to soften the impact of what is said next, implying that it is worthwhile or important.

   Coordinate terms: that said, well

   A: It's ridiculous how much they charge for insurance premiums around here. B: Not for nothing, when one out of four homeowners in an area has filed a claim within the past five years, premiums aren't gonna be cheap.

   • 2011, Stephen J. Cannell, Vigilante: A Shane Scully Novel, →ISBN:

     Listen, dawg, not for nothing, but I'm just horsing around with you when I say stuff like that.

   • 2012, Dayton Ward, Vanguard: In Tempest's Wake, →ISBN:

     And not for nothing, but I think you might want to talk to the doctor about a better diet. I suggest more fruits and salads.

   • 2013, John Vorhaus, Comedy Writing 4 Life:

     And not for nothing, but have you thought about going the indy-pub route, as I have with this book?

5. Used other than figuratively or idiomatically: see not,‎ for,‎ nothing.
   • 2010, F. J. Bradley, A Natural Place To Hide, →ISBN:

     Why did he keep writing all those years for nothing? Not for nothing. For him.

   • 2013, Mike Bird, Iskandar: And the Immortal King of Iona, →ISBN, page 238:

     Then, let us make sure that her death was not for nothing.