We are learning Latin! As a key, it switches the keyboard to letters. Abc is an identifier for the alphabet. The old Latin alphabet, in existence since 700 BC, comprised 23 instead of the current 26 letters.
Learn more about the meaning
Emoji History
Development of the emoji in the Unicode lexicon
First included
The emoji โInput latin lettersโ was approved as part of Unicode 6.0 in 2010 and added to Emoji 0.6 .