The present participle of 'gar,' meaning to prepare or make ready, or in some dialects, to snarl or growl.
From Old English 'gearu' (ready, prepared) or possibly related to 'gar' (spear), the word has dialectal usage varying by region. It may also relate to guttural sounds, hence the 'snarling' sense.
In some Scottish and Northern English dialects, 'garring' kept alive ancient Old English vocabulary that mostly disappeared—it's like finding a living fossil of the language in regional speech.
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