Late 18th century; earliest use found in John Sinclair (1754–1835), agricultural improver, politician, and codifier of ‘useful knowledge’. From concert + -ment.
Definition of concertment in US English:
concertment
nounkənˈsəːtm(ə)nt
The action of working or acting in concert.
Origin
Late 18th century; earliest use found in John Sinclair (1754–1835), agricultural improver, politician, and codifier of ‘useful knowledge’. From concert + -ment.