The meaning and origin of the expression: Swing the lead

Swing the lead

What's the origin of the phrase 'Swing the lead'?

I can recall that, as a child, I was attracted to an explanation of the phrase 'swinging the lead' that went like this:

Sailors used to use lines weighted with lead in order to check how deep the water was beneath their ships. The lazier mariners skimped on the task and just swung the lead in the air, calling out a fictitious depth.

Many years on and, as an etymologist, my heart doesn't exactly sing when I receive yet another email starting with "I've always believed that...". It seems time to revisit that explanation of 'swinging the lead' that I took on trust in my formative years and to check the facts.

A good place to start with research into nautical language is Admiral W. H. Smyth's The Sailor's Word-Book: an alphabetical digest of nautical terms, 1867. This is a glossary of the terms and expressions used by British sailors, most of which date from when 'Britannia ruled the waves', the 18th and 19th centuries. It is clear that sailors did indeed measure the depth of water by dropping in lines weighted with lead. The weights were called 'sounding leads' and Smyth includes this entry:

Lead, Sounding : An instrument for discovering the depth of water; it is a tapered cylinder of lead, of 7, 14 or 28 lbs. weight, and attached, by means of a strop, to the lead-line, which is marked at certain distances to ascertain the fathoms.

Deep-sea Lead: A lead of a larger size, being from 28 to 56 lbs in weight, and attached to a much longer line.

To Heave the Lead: to throw it into the sea as far ahead as possible, if the ship is underway.

The leads were sometimes hollow and filled with tallow wax, so as to bring up particles of whatever was on the sea floor, this being useful information to the ship's helmsman. The ropes were knotted at six-foot (fathom) intervals and sounding was also known as 'fathoming', that is. measuring in fathoms. This may be the source of the term 'fathoming out'.

The depth of water is crucial to sailors and, before the development of mechanical depth-sounders and, in the 20th century, SONAR echo-location, 'heaving the lead' was the only way of determining it.

[Another bane of etymology is the false acronym. SONAR is a genuine example of an early acronym, meaning 'SOund NAvigation and Ranging'.]

The leadsmen's role was important and physically demanding - they were called on to throw weights of up to 56 lbs into the sea and then haul them up at frequent intervals. The notion that they might have avoided the exertion of their task seems easy to believe. Counting against it is the fact that they would have had little opportunity for deception as they were supervised by officers and had to show the material that adhered to the tallow to the ship's navigator.

You may have noticed that, while Admiral Smyth mentions 'heaving the lead', he makes no mention of 'swinging the lead'. Indeed, until the early 20th century, nor did anyone else - the phrase is first recorded during WWI. In 1917, the magazine To-Day published this:1

"It is evident that he had 'swung the lead' (using Army phrase) until he got his discharge."

It's possible that the phrase was coined by soldiers in allusion to a supposed form of malingering by sailors. It may also be that 'swing the lead' was a corruption of 'swing a leg', which was a term previously used in both the British Army and Navy, with the same meaning. What is certain is that 'swinging the lead' wasn't used by sailors themselves in the days of sail.

And I had 'always believed that'.... At least my childish belief, although it appears now to have been overly gullible, did initiate an abiding curiosity about phrase origins.

See also: Phrases and saying coined at sea.

See also: the meaning and origin of 'Swing for'.