It is to leave your name or tag up somewhere. In today's
graffiti world it is a generalized term signifying earning a reputation by placing your moniker somewhere whither seen or not. Traditionally "to get up" meant to place one's
graffiti name in a high and visible location like a Billboard, Rooftop or High Rise i.e.
literally "Getting Up" somewhere high and visible in a sometimes difficult spot for notable and street fame.
Tonight I am "Gettin' Up" on that
Billboard along I-70 because I am Out for
Fame and
maybe one day I can earn some street credibility by "getting up" on rooftops like Amaze in L.A..