ink a deal

Origin

For centuries, the solemn act of signing a contract involved a quill or fountain pen, dipping into an inkwell to make a permanent mark on parchment or paper. This physical application of ink wasn't just a formality; it was the literal transformation of a spoken agreement into a legally binding, indelible commitment. To "ink a deal" thus became the definitive, decisive moment, signifying that all negotiations were complete and an agreement was officially sealed, moving from a handshake to a formal, unchangeable reality through the very medium of ink.