P van Rijckevorsel wrote:
Well, to me usage in this case is not very interesting since I already
have a fair idea:
- redcedar is a US term, and dominates the official documentation. It
refers to eastern, southern and western redcedar. This last is Thuja plicata
and will be the wood referred to by the general US populace as "redcedar",
"red cedar" or (especially, and by a comfortable margin) "cedar" whenever a
wood is being discussed.
- red cedar in the same official US documentation will be a cedar that is
red, or more particular has red wood. This will usually be Toona (fam
Meliaceae), yielding "Australian red cedar" and "Asian red cedar"

Beverly Erlebacher schreef
Here in Ontario we call Thuja occidentalis (eastern) white cedar and
Juniperus virginiana (eastern) red cedar. The intensely aromatic red
heartwood of the latter has long been used to make chests and line
closets to deter moths. North of the range of red cedar, people put
branches of white cedar in with woolen clothes to deter moths. White
cedar is sometimes called arborvitae here.

I've never seen "redcedar", only "red cedar", until this thread, FWIW.

+ + +
As I noted above "redcedar" is a US term and has its stronghold in the
official documentation. In everything I have of the USFS (Forestry Service)
this is used, but my set of USFS-publications does not appear to extend
further back than 1948.

It is also in the field guides, both the Audubon and Peterson. Or to be
accurate: of the three Peterson guides, all by the same author, the modern
ones (Eastern, 1988, 1998 and Western Trees, 1992, 1998) use "redcedar",
while the old one (Trees and Shrubs, 1958, 1986) uses "red cedar". In
Western Trees the author notes that he would welcome Canoe-cedar instead of
Western redcedar.

The average US-citizen uses "cedar" (when not used as a general category)
for Thuja plicata (western redcedar) and "aromatic cedar" for Juniperus
virginiana (eastern redcedar). The use of "cedar" is connected to the size
of the stands rather than to a particular tree.

To call Thuja "arbor-vitae" goes back quite some time (perhaps long enough
for Mike Lyle's dictionaries to have captured usage? :^).
PvR