I stray into a minuscule no-man’s-land of disputed territory here. On the one hand is a tiny group of language pundits who consider that ilk still ought to mean exactly what it used to mean centuries ago in another country. On the other hand is a greater group who know what they mean by it and don’t give a toss, fig, hang or tinker’s damn about its antecedents. On the third hand, a substantial group don’t know it, or are put off using it through worry that they might use it wrongly and have somebody criticise them.
Its story begins in Old English with the adjective ilca. This meant “same” or “like” and survived in mainstream English until the sixteenth century, in the end being supplanted by same, an upstart intruder from Old Norse. However, it did survive in Scots, especially in the phrase of that ilk. This meant, and still does, a person whose family name is the same as that of the place he inhabits. Most strictly it indicates that the person is the proprietor or laird of the place. So we may come across usages like this:
The field and ground was chosen in St. Andrews, and three landed men and three yeomen chosen to shoot against the English-men, — to wit, David Wemyss of that ilk, David Arnot of that ilk, and Mr. John Wedderburn, vicar of Dundee.
The Lady of the Lake, by Sir Walter Scott, 1810. Wemyss (said as weems), and Arnot are indeed places in Scotland, both in Fife.
But from early times, Scots also used it to refer to the head of a clan, even if the clan name wasn’t derived from a locality, such as Mackintosh of that ilk (a trial in Scotland in 1539 referred to “Duncane Macfarlane of that ilk”, where Macfarlane likewise isn’t a place name). This eventually led to ilk weakening its sense around the time of Scott to mean people who had the same name because they were related. It later weakened still further to include people of the same class or who had some characteristic in common. This much broader connotation annoys language purists, though it has long since become common and is now regarded as standard English:
I’m pretty no-nonsense myself, and I know plenty of other women of that ilk.
Daily Telegraph, 4 Apr. 2015.
These days the grouping need not always be human (“Such are the magpie, the crow, the jackdaw, and all of that ilk”; “it wasn’t a unicorn, but it was something of that ilk”) nor even alive (“She discovered the ace of that ilk peeping coyly out from behind the seven of spades”; “A body may chatter about ideals — about right and wrong and matters of that ilk”).
A blurred survival of its aristocratic, landed origins sometimes emerges in negative comments about class bias:
Given that David Cameron seems to be comfortable only when surrounded by Etonians, and that the Labour MP Chris Bryant has complained about “Eddie Redmayne and James Blunt and their ilk” rising in their professions thanks to their privileged public-school education, a toff upbringing doesn’t feel terribly cool or right-on at the moment. Lewis is definitely a member of that “ilk”.
Sunday Times, 12 Apr. 2015.