From Middle English hoo, shoo (“she”) from Old English hēo (“she”). More at she.
Meanings
(Derbyshire, Yorkshire, feminine, nominative, qualifier:South Lancashire, singular, third-person) she
'Aye, aye,' said the father, impatiently, 'hoo'll come. Hoo's a bit set up now, because hoo thinks I might ha' spoken more civilly; but hoo'll think better on it, and come. I can read her proud bonny face like a book. 1854, Elizabeth Cleghorn Gaskell, North and South, Chapter VIII:
(England, South, West, West-Midlands, feminine, nominative, singular, third-person) he, also a gender-neutral third person pronoun
(obsolete) Expressing joy, excitement, or victory.
With, hoo! such bugs and goblins in my life c. 1599–1602 (date written), William Shakespeare, “The Tragedie of Hamlet, Prince of Denmarke”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):
Our enemy is banish'd! he is gone! Hoo! hoo! c. 1608–1609 (date written), William Shakespeare, “The Tragedy of Coriolanus”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):
(Geordie) Used to attract the attention of others.
"Hoo yee!"
An exclamation of pain.
Old Peter, summoned to assist at getting Mrs Dibble upstairs, made no pretence of commiseration for the sufferer. "Gone and done it again, have you?" he said with satisfaction. "About the best thing you could have done, the way it'll keep you out of the shop a bit longer," which so far revived Mrs Dibble that she exclaimed fiercely, "I don't want none of your cheek, Peter Bodfish and not a minute you'd stay in my shop if - Hoo! Ow! Me leg - " 1950, Norman Lindsay, Dust or Polish?, Sydney: Angus and Robertson, page 98:
Improvising a stretcher from a cupboard door, they levered Mrs Dibble on to it and got her upstairs to "Hoos!" and "Ows!" of anguish, and laid her on the bed, where Rita administered another stiff dose of gin. 1950, Norman Lindsay, Dust or Polish?, Sydney: Angus and Robertson, page 98: