Loonie and Toonie. (The latter also has two alternate spellings - Twonie or Twoonie - neither as popular, however.)
The Loonie is named after the Loon bird that is on many of these coins. Interestingly, issues of that coin that contain other designs, and don’t have a picture of the Loon, are still called "Loonies":
Loonie & Toonie.
Loonie and Toonie. (The latter also has two alternate spellings - Twonie or Twoonie - neither as popular, however.)
The Loonie is named after the Loon bird that is on many of these coins. Interestingly, issues of that coin that contain other designs, and don’t have a picture of the Loon, are still called "Loonies":
http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20070627/canadian_loonie_070627/20070627?hub=Canada
Background on the Toonie’s naming:
http://en.wikipedia.org/wiki/Toonie#Naming