On the field, the Detroit Lions are always trying to defend their home field. Off the field, they are working that into one of their main slogans.

ESPN Business reporter Darren Rovell reported the Lions registered the trademark for “Defend the Den” on Nov. 10, 2015, after filing to trademark the slogan on April Fool’s Day last year.

It is not the only phrase the Lions have trademarked recently. ESPN.com has found the Lions trademarked "One Detroit One Pride," filing for the trademark on April 23, 2015, and getting the trademark registered on Dec. 15 for clothing and T-shirts as well as stadium use.

The "Defend the Den" phrase has been a constant around Ford Field the past two seasons. It is often on their big screens at the stadium and has been their main slogan outside of Ford Field.

It’s not the most original phrase and has been used many other places. The AHL’s Hershey Bears have used it for promotional materials, T-shirts, slogans and Twitter hashtags since before the Lions started using it.

Montana State football used it for its ticket packages. Christ Presbyterian Academy in Nashville uses it for the school’s anti-bullying campaign and the Blake School in Hopkins, Minnesota, uses it for sporting events.

It isn’t the only phrase the Lions use often -- “One Pride” has been all over Detroit’s signage and was on the cover of the team’s 2015 media guide. But Defend the Den has been a big rallying cry for the Lions since Lewand introduced it in 2014 as a Lions slogan.