An obsolete (Middle English) or dialectal (Scotch) form of holy.
The Century Dictionary (Public Domain)
Use "haly" in a sentence
""Just that," said he, solemnly, "a guid man an 'haly' was auld Paul."
"I'm sad that Robert English isnt in it but I can't wait to see what haly joel osmaond does with the character of freddy couger."
"The pepil richt affrayitly, returnit to him out of all partis of the wod, to comfort him efter his trubill; and fell on kneis, devotly adoring the haly croce; for it was not cumin but sum hevinly providence, as weill apperis; for thair is na man can schaw of quhat mater it is of, metal or tre."