What purpose did "道搿" serve? I was flipping through The Hanyu Da Cidian when I came across an entry for the word:


  道搿
  dàogé


the definition is as follows:


  英语dog的音译。谓狗。


and they provide the reference:


  《文明小史》第三五回
  ﹝毓生﹞却回到屋裏, 拍桌大駡道：‘ 中國 的官這般没信實, 還不如外國的道搿哩。’一個夥計嘴快, 搶着説道：‘掌櫃的, 這話錯了。難道你認得外國的道搿麽？’ 


Chinese obviously has a word for dog &amp; it's clearly written in Hanyu Da Cidian's definition above: 狗. 道搿 doesn't seem to add anything to the word that isn't already there. The fact that 道搿 exists at all though does show that there must have been some sort of need for a word as such. 

What purpose did "道搿" serve?
The fact that it is a transliteration of English "dog" points to its possible use and appearance. Perhaps, it was used for those foreign breeds of dogs that looked different from the breeds that Chinese people were accustomed to at that time (end of Qing dynasty).

But also note that this particular word (道搿) does not seem to appear in any other text than the mentioned novel (文明小史). So it might have been simply the novelist's invention, that the authors of Hanyu Da Cidian still felt they needed to explain. (Mind you that this dictionary was compiled before widespread use of corpus linguistics, so the authors wouldn't really know if this word is just a one-time appearance across all of the Chinese literature, or if it got some traction and started to be used by others.)