No, not the gastropod that wreaks havoc in my garden, but a unit of mass: from Wikipedia:

The slug is an English unit of mass. It is a mass that accelerates by 1 ft/s² when a force of one pound-force (lbf) is exerted on it. Therefore a slug has a mass of 32.17405 pound-mass or 14.5939 kg

Anyone any idea why it was called a slug?

Incidentally, whilst looking at the various meanings of “slug”, I was interested to discover that “sluggish” does not derive from “slug” (the beast) and the name of the beast is relatively modern. I wonder what they were called before the C18th.

bayard - 12 February 2009 12:52 AM

Incidentally, whilst looking at the various meanings of “slug”, I was interested to discover that “sluggish” does not derive from “slug” (the beast) and the name of the beast is relatively modern. I wonder what they were called before the C18th.

‘Worm’ covered all sorts of creeping crawling creatures at this time and well before. OED doesn’t specifically give it as a name for a slug but the chances are good.

Slug as a unit of mass probably comes from the use of ‘slug’ for a lump of crude metal

Shakespeare in 1594 used the word alongside “snail” in The Comedy of Errors II II lines 169/170.
Why prat’st thou to thyself and answer’st not?
Dromio, thou drome, thou snail, thou slug, thou sot!

This doesn’t prove that he was referring to the garden slug, but it is suggestive.

Have we seen the Shakespeare Insults Generator yet?  Here it is anyway.

Yes, the unit of mass almost certainly comes from the slug of metal. The official name slug for the unit of mass was proposed by an A.M. Worthington in 1902.

The slug of metal probably comes from the sense meaning a slow-moving object. The original sense of slug in English was that of a lazy, slow-moving person. This sense also gave birth to the slow-moving gastropod. The word appears to be a 15th century borrowing from either Swedish or Norwegian.

Shakespeare in 1594 used the word alongside “snail” in The Comedy of Errors II II lines 169/170.
Why prat’st thou to thyself and answer’st not?
Dromio, thou drome, thou snail, thou slug, thou sot!

This doesn’t prove that he was referring to the garden slug, but it is suggestive.

It is, though the following “sot” lessens the force of the suggestion somewhat.

The OED does not cite that passage in illustrating any of the senses of “slug”, though they do cite it under “snail” (in the sense “A slow or indolent person; a sluggard"). Their earliest citation for the gastropod sense is from 1704, which casts some doubt on the idea that Shakespeare was referring to the garden slug.

Interesting, though.

Eng ‘slug’ very much resembles Dutch ‘slak’ (used for both snail and slug), but both WNT and Van Dale don’t connect them. (EWN hasn’t published the S yet) WNT suggests it is related to Du ‘slijk’ (mud, cf. NE ‘slick’). Remarkable is that there is another Du ‘slak’ used for piece of waste from metal forging. It’s not related to the other ‘slak’, but to Dutch ‘slaan’ (to beat). Again apparently no connection with its English counterpart. Since the two English words appear related, it means there are three different etymologies involved. Strange case of parallel evolution, I’d say.

The Afrikaans word for hit is slaan, and the word for beating someone to a pulp is slaat.

A slug, for us old letterpress typesetters, is also a strip of metal 6 points wide.  There are 72 points to an inch.

Remarkable is that there is another Du ‘slak’ used for piece of waste from metal forging. It’s not related to the other ‘slak’, but to Dutch ‘slaan’ (to beat).

Could the Dutch “slak” (in the metallurgical sense) be related to “slag” meaning the siliceous residue from smelting metals? (I’m not quite sure, dutchtoo, what you mean by “residue from metal forging”, which suggests scrap metal, rather than scoria).

The derivation of “slak” which you mention, from a word meaning “to beat”, is probably related to the English “slog”, one of the meanings of which is “to strike heavily” (it’s used in that sense in the game of cricket: a “slogger” is a batsman with more fury than style)

I’ll add another set of related words: sly (English), schlau (German)

Grimm says that the German is of uncertain origin, but suggests that it might rest on the idea of adroitly striking (schlagen) in battle.

Actually, Lionello, I had been struggling with the translation of a definition in one of my dictionaries. This was version six or so. Sorry I couldn’t make it any clearer. Looking for a good description, I came across this website that describes aluminium casting in Dutch and English. It uses ‘slak’ alongside English ‘slag’ rather than ‘slug’ so I’m beginning to believe that ‘slak’ and ‘slug’ may not be entirely the same. Although Van Dale explains the etymology of ‘slak’ as ‘pieces of metal, flying off by beating’, the common meaning is that of ‘residue from melting’, for which I think ‘scoria’ would be a better word. OTOH we can now add English ‘slag’ to the list, about which Etymonline has this to say.

In this context I would also like to mention Dutch ‘slaag’ meaning ‘a beating’ and ‘slag’ meaning ‘stroke’.

And while we’re at it, under ‘slug’ I found this on Etymonline:
meaning “strong drink” first recorded 1756, perhaps from slang fire a slug “take a drink,” though it also may be related to Ir. slog “swallow.”

This immediately brought Dutch ‘slok’ to mind. It means ‘a mouth full to swallow’ and by extension ‘a strong drink’. Again, apparently not related. It’s from Dutch ‘slokken’ (to swallow).

The Dutch cognate of NHG ‘schlau’ is ‘sluw’ for which my dictionaries don’t give an etymology but it appears to be related to a group of words including Du ‘sluipen’ and ‘sluiken’ (to sneak).

A fruitful combination of sounds, it seems.