Equivalent in seriousness to; virtually the same as.
Mid 17th century: from the earlier verb tantamount ‘amount to as much’, from Italian tanto montare.
“His reaction is tantamount to guilt, he may as well have confessed.”
Nothingburger (noun) (Chiefly US)
A person or thing of no importance, value, or substance. Now esp.: something which, contrary to expectations, turns out to be insignificant or unremarkable.
1950s: from nothing and burger. Added to the OED October 2018.