Plural form, possibly referring to multiple booleys (pastoral settlements) or a dialectal/variant form.
Likely a variant plural of 'booley' (Irish/Scottish pastoral settlement), with '-ies' instead of '-eys' as the plural ending.
English plurals are messy—we have 'booley/booleys' and 'boolie/boolies' existing side-by-side, showing how the same Gaelic word got adopted differently in different regions.
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