Friday’s Phrase – Sweat Like a Pig

Welcome to the weekly series “Friday’s Phrase”. A whimsical and informative look at the idioms, phrases, proverbs and colloquialisms we commonly use, what they mean, and where they came from.

This week’s phrase:      “sweat like a pig

This is another favorite. I use it often as, for me, I can begin to sweat just thinking about doing something strenuous. I continued to use it even after I had learned that, although pigs do sweat, it is in such small amounts as to not be effective. That is why they wallow in dirty water and mud. So, the reference made even less sense then it did when I thought pigs were exceptional at perspiring.

Current accepted meaning:


1. To sweat profusely; to perspire with little effort.

“I start to sweat like a pig within seconds of stepping on a treadmill, but you walk out of the gym after a workout like you’ve been just sitting at a desk.”


Historical Recorded Use:

The earliest record that I have found is from The Morning Post (London) of November 10, 1824, reporting a boxing match between Ned Turner and Peace Inglis, where the writer says of Inglis, “He sweats like a pig”.


My original error here was thinking that ‘pig’ meant ‘swine’.

The truth is that the term ‘pig’, in this context, is in reference to the smelting process of producing a metal from its ore — in this case, iron ore. As part of the process to produce steel, iron ore is smelted into something called ‘pig iron’. Pig iron is a brittle version of iron which, because of this trait, has limited uses. But because it is just going to be melted again to produce steel, it does the job. It gets its name from its traditional shape, which resembles vaguely a group of piglets attached to their mother.

When pig iron is originally created from iron ore, the smelter needs to heat the ore to extreme temperatures, and then move the liquid metal into the mold. Until the liquid cools, it can’t be safely moved, as the extremely hot metal is liable to spill, burning anything it encounters. How does the smelter know when the metal is cool enough to transport? When the ‘pigs’ ‘sweat’. As the metal cools, the air around it reaches the dew point, causing droplets to form on the metal’s surface.


There is some argument to how a technical expression originating in limited circles would give rise to a popular phrase. Some detractors argue it comes from an Italian simile appearing in a letter from Naples, dated April 15, 1826, but no evidence supports this connection, and it would still leave the origin open to that stated above. Since smelting had occurred more than 200 years prior to the first printed use, it is easy to surmise that in that period of time the phrase could have easily moved into common language.

Bonus Phrase: (provided at no extra charge)

The term ‘pig’, in true reference to the animal, is found in many other derogatory idioms that represent its perceived nature, all of which are self-explanatory:

‘eat like a pig’
‘make a pig of oneself’
‘happy as a pig in muck’

One Response to “Friday’s Phrase – Sweat Like a Pig”
  1. I suspect 99.9% of us stand corrected in learning that it is not an animal reference! Fascinating!

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