sled vs troika

sled

noun
  • A vehicle on runners, used for conveying loads over the snow or ice. (contrast "sleigh", which is larger) 

  • A small, light vehicle with runners, used recreationally, mostly by children, for sliding down snow-covered hills. (A "sled" in this sense is not pulled by an animal as a "sleigh" is.) 

  • A snowmobile. 

verb
  • To ride a sled. 

  • To convey on a sled. 

troika

noun
  • A Russian carriage drawn by a team of three horses abreast. 

  • A party or group of three, especially a ruling council of three people in Russian contexts. 

How often have the words sled and troika occurred in a corpus of books? (source: Google Ngram Viewer )