Final ‘th’ was regularly not pronounced in some dialects, notably in a suffix such as ‘forth’, so ‘garr’ was a characteristic regional spelling of ‘garth’.
In general usage a 'gate' is a form of barrier, a door, set across a gap in a wall or hedge, and it can be opened to allow people and animals to pass from one place to another.
In numerous northern land deeds the word ‘gate’ referred to a right for animals such as cattle, horses, sheep and swine to ‘go’ onto certain grazing lands, it was a right to pasturage.
A regional spelling of gable, defined in the OED as the triangular piece of wall from the eaves to the summit, although colloquially the ‘gable end’ seems to refer to the whole wall.
To geld was to castrate a male animal and this was a significant and necessary operation in animal husbandry, especially for institutions such as the great monasteries which had large flocks and herds.