We must have had an era of 'parents hanging stupid names on their kids' of which I was totally unaware.
Half the fun of watching college football games these days is to LOL/shake head incredulously at what some of those young people are called.
Justus is a late Roman name, and it was given to many Popes some centuries ago. It also appeared in the Dutch language as “Joost” or “Jost.” It means “just” as in “fair” or “unbiased.” It is NOT dialect or a misspelling for “justice.”