The title illustration from the first edition of Troy Town by Sir Arthur Quiller-Couch, in which pillaloo is shouted.
The Oxford English Dictionary tells us pillaloo began its life centuries ago as a hunting cry, taken from the Irish puilliliú.
Among its appearances was that in 1888 in The Astonishing History of Troy Town by Q (Sir Arthur Quiller-Couch), though you might have some difficulty picking the sense out of his representation of the local Cornish speech:
An’ the wust was, that what wi’ the rumpus an’ her singin’ out “Pillaloo!” an’ how the devil was amongst mun, havin’ great wrath, the Lawyer’s sarmon about a “wecked an’ ’dulterous generation seekin’ arter a sign” was clean sp’iled.
Henry Murray’s usage in Lands of the Slave and the Free of 1857 is very much easier on the modern eye and ear; he uses it in the alternative Irish English sense of a cry of distress:
The dialogue was brought to a sudden stop by the frantic yell of the juvenile pledge of their affections, whose years had not yet reached two figures; a compact little iron-bound box had fallen on his toe, and the poor little urchin’s pilliloo, pilliloo, was pitiful.