Crowninshield, along with its less-common variant Crowningshield, is a surname used by descendants of Dr. Johannes Kaspar Richter von Kronenschieldt II, a Danish-German doctor who arrived in Boston in 1688 and became the progenitor of one of the city's most socially-prominent families.
The name "von Kronenschieldt" means "of Kronenschieldt." "Kronenschieldt" itself roughly translates as "crown in/on shield." (The Crowninshield coat of arms features, fittingly enough, a crown on a shield.) Kronenschieldt was a village outside of Leipzig, Germany where the Richter family of Denmark (originally Sweden) had settled during the Thirty Years' War.