The Old English pronoun ilca is the predecessor of the modern noun ilk, but by way of a pronoun ilk that does not exist in most dialects of modern English. That ilk is synonymous with same, and persists in Scots where it's used in the phrase of that ilk, meaning "of the same place, territorial designation, or name." It is used chiefly in reference to the names of land-owning families and their eponymous estates, as in "the Guthries of that ilk," which means "the Guthries of Guthrie." Centuries ago a misunderstanding arose concerning the Scots phrase: it was interpreted as meaning "of that kind or sort," a usage that found its way into modern English. Ilk has been established in English with its current meaning and part of speech since the late 18th century.