n. — Food
a powdered sugar containing a small amount of cornstarch; confecctioner's sugar.
The term icing sugar describes a type of finely powdered sugar (see the 1885 quotation) that is combined with cornstarch to prevent clumping. The term appears to derive from the product's main use, which is to make icing for cakes or baked goods (see the 2013 quotation) or to dust them with sugar (see the 1893 quotation). The term is more frequent in New Zealand, Australia and South Africa than in Canada (Chart 1). While icing on a cake (vs. US frosting on a cake) is a Canadianism (see icing (3)), icing sugar is not. Confectioner's sugar is the Canadian name, in the sense of the DCHP-2 typology, for the sugar itself (see Chart 2).
See also COD-2, s.v. "icing sugar", which is marked "Cdn, Brit., Austral. & NZ".
See also: berry sugar confectioners sugar icing ((3))
- 1885  A friend writes that the pulverized sugar we mentioned on page 563 is not obtainable in his section. Very often it is called "icing" sugar. If your grocer does not keep it, he can soon obtain it of any wholesale house, and he will no doubt be glad to do so if you intimate your deisre to have it. 
- 1893  Drain them well, lay them on a baking tin, dust them with icing sugar, pass a red hot shovel over them to glaze them, and serve at once. 
- 1930  Take hot cooked sweet potato and mix with the icing sugar. Flavor with almond extract. 
- 1942  Sweetened condensed milk makes a marvellous fudge, with a comparatively small amount of icing sugar (you can spin it out for home use by using some crushed vanilla-wafer crumbs along with the sugar, if you like). 
- 1957  Hang a Maurice Prior painting on your wall and, if you get tired of looking at it, you can always eat it. Maurice, executive chef at the Granite Club of Toronto, paints in icing sugar. [...] Painting in icing sugar is a tricky procedure, says Maurice. Not only is it necessary to mix to exactly the right color, but also to the right consistency. 
- 1976  BLEND butter, egg yolk, icing sugar, orange rind and enough orange juice to make an icing that is easy to spread. 
- 1983  Camille Mitchell plays the new arrival, Rhoda, with a sweet and angelic innocence that seems to be spun from icing sugar. In fact, she seems more like a cake ornament than a girl as she wafts from place to place and curls up on top of the nearest table or sofa back rather than sitting down like anyone else. 
- 1990  Police were forced to move in prematurely after three people in Montreal decided to sample the fresh cocaine shipment destined for New York and got noses full of icing sugar instead, sources said. 
- 2002  What caused the duck to act this way? Does she have a gene right next to the flying V gene that programs the duck to seek out a human with shiny belt buckles and icing sugar in his moustache when in trouble? Or is it just instinct? 
- 2013  For icing: Mix together one-quarter cup of icing sugar and one tablespoon of whipping cream or milk, and half a teaspoon of vanilla. Spread over buns. 
Images:
Chart 1: Internet Domain Search, 4 Jul. 2014
Chart 2: Internet Domain Search, 4 Jul. 2014