"Drywall compound" is used to fill in the gaps between sheets of gypsum wallboard. In the trade this is referred to as "mud". At first I thought this was modern slang, but I am wondering whether the word has been continuously used in the plastering trade since back when it actually was mud.
Mud and plastering go 'way back' to ancient times, when mud was actually used as mortar, plaster, and the basis of mud bricks.
But the actual use of the English word 'mud' is a little more interesting, and perhaps most of all in that it's common use as a term for mortar for bricks ('brickies mud' in Australia) is largely unacknowledged.
Firstly, the OED on 'mud' in the sense of plaster:
d. mud and stud (dial.): posts and laths filled in with mud, as a material of which walls of cottages, etc., are built (also stud and mud: see stud n.); similarly mud and log, mud and reed, etc.
1839 Stonehouse Axholme 389 The rectory house was an old fashioned dwelling, with high gables and walls of mud and stud. 1843 Marryat M. Violet xxxii, The miserable twelve-feet-square mud-and-log cabins. 1900 Daily News 18 May 6/2 The mud and reed towns of the negro.
But as plaster became a much more refined mix of gypsum, lime or cement, the name 'mud' stuck, but only in the sense of a wet plaster mix of good consistency prior to application. So there are mud mixing tools, mud carrying tools, instructions for mixing and applying mud. But one no longer refers to dried plaster as mud.
Again references are scarce, but the OED has an interesting variant:
mudding mudding, vbl. n.
[f. mud v.1 + -ing1.]
1. a. The action of making muddy.
1632 Sherwood, A mudding, beraying with, or sticking in mudde, embourbement, enfangement. 1635 A. Stafford Fem. Glory (1869) 179 The mudding of their purest Fountaine. 1895 H. P. Robinson in Forum (N.Y.) Jan. 528 The mudding of the stream in æsop's fable.
b. The filling of cracks in the walls of a house or log-cabin with mud. Canad.
1898 F. Russell Explor. Far North 2 The autumnal ‘mudding’ was poorly done. 1965 E. L. Myles Emperor of Peace River ii. iii. 209 On the exterior of the logs treatment was a must if the rooms were to be warm in winter. This treatment consisted of an annual ‘mudding’, the forcing into the chinks between the logs of a mixture of mud and straw.
2. A jocular term for: Plastic work, modelling.
1892 Stevenson & L. Osbourne Wrecker 6 ‘The daubs are mine—and his; the mudding mine.’ ‘Mudding? What is that?’ asked Havens. ‘These bronzes,’ replied Dodd.
Colloquial usages are hard to find in print. I would suspect this is partly to do with the fact that once instructions relating to the mixing of materials for modern building find themselves in print format, they are very particular about the language they use, in order to precisely indicate what is being referred to, and to clearly differentiate products and mixes that might otherwise simply be referred to as 'plaster', or indeed 'mud'. One rare example of a manufacturer lapsing into the vernacular on a sales broadsheet:
Mortar is a mixture of Sand, Cement, Water and Lime. Mortar acts as the bonding agent between bricks and blocks, as well as the medium that accommodates variations in their dimensions. This page provides suggested mortar mixes and the amount of brickies mud required for your home project. (referring to brick mortar from http://www.boral.com.au/packagedproducts/packaged_products_tips.asp)
Older examples of the use of the term 'mud' for plaster are hard to track down, and the waters are muddied somewhat by a plethora of modern and ancient references to mud brick and earth wall construction (in which case 'mud' simply refers to mud). Diligent seaching, however, is likely to turn up some good examples.
The paths back from, and leading up to, the usage of the term 'mud' for wet plaster or mortar are probably too complex to untangle. The trades person/builder (or more likely the apprentice to that person) who mixes the 'mud' for the skilled plaster or brick layer probably finds the use of the term 'mud' entirely natural for something that looks like mud, is as hard as mud to stir, and as heavy as mud to carry. This use might find itself authentically (and unambiguously) expressed in fiction that reflects the 'street talk' of builders. In another sense, there is a 'nod' to the ancient plastering methods in the use of the term, but it would me most interesting to find it in use in that sense in very early references to the art of plastering. But in a final, confounding sense, there is a continuous progression of thought (and language) applied to the seeking out and preparation of materials for plastering that does go all the way back to mud, and concurrent use of older and contemporary materials and techniques even down to the modern age where counter-culture building exponents might employ techniques of mud building not unfamiliar to stone-age Britons or ancient Sumerians.