Vessels for liquor such as Nihon-shu[日本酒（にほんしゅ）](sake, rice wine) are called "Sakazuki[盃（さかずき）]". And Choko[猪口（ちょこ）] or Ochoko[御猪口](O[御] is a polite prefix) refers to small-size Sakazuki. But Sakazuki also refers to smal-size, shallow and wide vessel. Therefore, in particular, the term "Choko" is something other than that.
Most Chokos are made of ceramic but there are Chokos made of glass. Choko is also used as a vessel for dishes.
There is a white Choko which a double blue circle, which is called "Jyanome[蛇の目（じゃのめ）](snake eye)", is depicted on the bottom. This pattern is for examining the transparency of Nihon-shu by seeing the clearness of the border of white and blue color. Hereby, the taste can be guessed.
And a Choko for soup of Soba[蕎麦（そば）](buckwheat noodle) is called "Soba-choko[蕎麦猪口（そばちょこ）]". When eating cold Soba, that is dipped into the soup in a Soba-choko.
Choko is small and if you drink Nihon-shu from Choko, you may drink it up soon. Therefore, Nihon-shu is served in a tall vessel called "Tokkuri[徳利（とっくり）]" when drinking it from Choko.
And large-size Choko is called "Guinomi[ぐい呑み]". When drinking Nihon-shu from that, Tokkuri is not used.
Tokkuri is also used for pouring the soup of cold Soba into Soba-choko. That Tokkuri is called "Soba-dokkuri[蕎麦徳利（そばどっくり）]".
The term "Ochoko" is used as a metaphor for a small-hearted person. And that also refers to inside out umbrella.