In this case, I, probably, would have been better off saying something like "City Guard" for clarity because "home" is a shortening of "hometown," which is referring back to Empress Síria I's birth in Kelsium. Their inference is that there'd be no Empire if she hadn't united all of the sargons. Thus, a future Empress stationed the legion there as a tribute to Síria.
Edit: The Legion's official name is, actually, I Kelsí (1st Kelsian). However, residents of the Empire have appended it with the nickname (cognómen?) Custódia patria (hometown guard), at the very least. I'm playing with the idea of having them put the adjectival form of Síria's name into the nickname to quash any ambiguity, making the nickname Custódia patria Sírína (guard of Síria's hometown. Would patria be capitalized? I think it would start with a lowercase letter but want to make sure.