This was the original question posed on the History of Economics discussion thread:

I am researching the debates over the Ten Hours Bill in 1844. One of the disputants observed 5 mills, spinning

“No. 14, 15, 30, 38, and 40 yarn”

These numbers are calculated by measuring the length per unit of weight of the cotton spun. I can’t find what unit of length and what unit of weight was employed (the larger the number. the finer the yarn). Any ideas?

The discussion then revolved around something I recall from my youth, which is the “denier”, pronounced, as I also recall, “den-yair”. Which led to this post, since I hadn’t even noticed the alternative current meaning as the discussion wandered along.

I remember now — hosiery ads (and maybe bed-linen ads?) used to say “21 denier” and I had no idea what that meant.

No idea how to pronounce it, either. One on-line dictionary says to pronounce it DENN-yer.

I put the word into Google Ngram Viewer and after a century of noise, the graph suddenly leaps up after 1940, to a peak in 1950 three times higher than the secular background level. Then it falls back to the secular level by 1960. I would guess that this reflects the use in hosiery ads (etc.).

More recently we have “global warming denier” and the like. I don’t suppose the ngram viewer can distinguish that meaning, if we search for only the one word and not some contextual phrase. But by default the viewer stops at the year 2000.

But what I found fascinating was that the original poster finally explained what the numbers had meant, which had nothing to do with “denier” in the measurement sense:

Thanks for all of the helpful suggestions. It turns out that this is not a “denier system” That is a direct-management system where the smaller the number, the finer the thread. Instead, Manchester employed an “Indirect System”. The numbers are sizes, that is the length of yarn (in yards) needed to reach a weight of one pound. Thus the higher the number — 14, 15, 30, 38, 40 — the finer the yarn or thread.

Scholarship at its best.