At the rally Trump said "MS3" instead of MS13 one time. Maybe just misread the prompter. Throwing it out there in case it was not a mistake and comes up again somehow.

ms3-inc.com
Cloud Integration Solutions

ms-3.co.uk
MS3 Networks is a fibre network operator

https://en.wikipedia.org/wiki/MS3
Mighty Servant 3,is a 27,000 ton semi-submersible heavy-lift ship
MS3 can refer to Mississippi's 3rd congressional district or Mississippi Highway 3