Fig. to unite or assemble in support of someone or something. All the other workers rallied around Fred in his fight with management.They rallied around the principle that Fred stood for.
Join in a common effort, as in When Mom broke her leg the entire family rallied around to help. This idiom gained currency with George F. Root's famous Civil War song, "The Battle Cry of Freedom," which urges troops to rally round the flag that goes with them into battle. [Early 1800s]