That is the name that William Penn gave it when he founded it.
Paddy's Irish Pub
The name Philadelphia comes from Greek, meaning "Brotherly Love", hence one of Philadelphia's nicknames is "The City Of Brotherly Love"
William Penn planned the layout of the city himself. It was based on a logical grid pattern and based around four town squares and would lie between the Delaware and Schulykill (pr. skoo kill) rivers...
It was named by William Penn.
"Michael Anthony Nutter"