Anglicized spelling of Síle, the Irish Gaelic form of Cecily. This name has become so common and widespread that it is hardly felt to be Irish any longer. In Australia since the 19th century it has been a slang generic term for any woman.
German: either from an Old Prussian name of uncertain origin, or a shortened form of Pehlemann, a habitational name from a place called Pehlen near Detmold. Alternatively, it could be a shortened form of North German Pehlgrimm ‘pilgrim’ (standard German Pilger).