1) An enclosure where young trees were grown, possibly a kind of specialist market garden or plantation.
In Old English impa had to do with the young shoots of plants and then of grafted shoots, and it clearly retained those meanings into the post-Conquest period. Indeed, imp yards were once a common feature of the English landscape, certainly in the northern counties where the place-name is quite common. A Durham imp yard is quoted in the OED for 1337-8, but it may be the only reference in the dictionary. Early Yorkshire examples include: 1366 Imposyearde [sic], Methley
1380 le Ymppezherd, Aughton
1385 le Impezerd, Rotherham. In more northerly parts of Yorkshire, and in other northern counties, an alternative term which had the same meaning is imp garth, and examples there take the word back even further. They include c.1250 Ympegard’ in Cumberland and two instances in Yorkshire: 1259 Impegarde, Follifoot near Harrogate
1454 the ympegarth, Kirkby Malham. The inference is that imp yards were originally enclosures where young trees were nurtured, possibly a kind of specialist market garden or plantation. That is partly confirmed by a document dated 1414 which records the indictment of a Methley man called John Cook: he was accused of stealing wood from the Impeyeardes that belonged to the lord of the manor, and the clerk conveniently added the words ‘to wit young oaks’, so it is clear that the offender had been stealing saplings. We do not know how old a term imp yard is nor when it began to fall into disuse, but several examples quoted above occurred in contexts which suggest that it may have been in decline by the 1500s. That is implicit in the field name Cowe close otherwise ympyarde, listed in the Dissolution survey for the priory of Hampole in c.1540. Some sites can still be identified: in Kirkburton, for example, a terrier of the glebe lands in 1684 included a meadow called Imp-yard which butted on the graveyard at its southern end. It is mentioned in later terriers but cannot be found on maps which date from 1753. However, the boundaries of the glebe lands are shown, so we know that the present extension to the cemetery marks the site of the former ‘imp yard’.