Adelphi

popular name of a diverse group of marine mammals, also including the porpoise (but the true dolphin has a longer and more slender snout), mid-14c., dolfin, from Old French daulphin, from Medieval Latin dolfinus, from Latin delphinus "dolphin," from Greek delphis (genitive delphinos) "dolphin," related to delphys "womb," perhaps via notion of the animal bearing live young, or from its shape. Popularly applied to the dorado from late 16c. through some confusion. The constellation is so called from early 15c.

city in Pennsylvania between the Delaware and Schuylkill rivers, from Greek, taken by William Penn to mean "brotherly love," from philos "loving" (see philo-) + adelphos "brother" (see Adelphi). Related: Philadelphian.

Also the name recalls that of the ancient city in Lydia, mentioned in the New Testament, which was so called in honor of Attalos II Philadelphos, 2c B.C.E. king of Pergamon, who founded it. His title is said to have meant "loving the brethren" or to be a reference to his affection for his brother Eumenes, whom he succeeded.

Philadelphia lawyer "clever, shrewd attorney" is attested from 1788 in London, said originally to have been applied to Andrew Hamilton, who obtained the famous acquittal of J.P. Zenger in New York on libel charges in 1735.

[C]ricket and coaching were after all popular in their day in places besides Philadelphia. It was merely that Philadelphia kept on with them longer than most places. This is a perennial Philadelphia trick, and gives to Philadelphia a sort of perpetual feeling of loss. Philadelphians are always just now getting rid of things that are picturesque, like those gas lamps on the streets, only because everybody else got rid of them long ago. [Nathaniel Burt, "The Perennial Philadelphians," 1963]