In my family tree, I’ve noticed the name Loreto/Loretto as a girl’s middle name from about 1860. It seems to peak around 1900 or so (though there are a couple of examples which occur a generation or two later).
So, for example, my great-grandmother, daughter of Patrick Killeen and Bridget Galligan, was baptized Bridget Loreto Killeen on 11 Jun 1861. Her first cousin, daughter of John Killeen and Margaret Fahey, was baptized Celestina Loreto Killeen on 28 Mar 1871. Her second cousin, daughter of Thomas Daniel Galligan and Catherine Brady, was baptized Helen Loreto Galligan on 20 Apr 1896. Her husband John James Lahey’s second cousin, daughter of Thomas Armstrong and Henrietta Charlebois, was baptized Bridget Loretto Armstrong on 29 May 1898 (this Bridget Loretto is also connected to my father’s family through at least one other branch).
I had initially assumed that the name referred to the Marian shrine in Italy. However, given that the above were all Canadian Catholics of Irish origin, it seems at least as likely that the name was chosen with reference to the Loretto Sisters who first arrived in Canada in 1847.