“The Helvetii, a Celtic tribe who battled Julius Caesar, gave their name to the Swiss territory. The Latin name for the country, Helvetia, still appears on Swiss stamps. The letters CH appearing on Swiss cars and in internet addresses stand for the Latin words Confoederatio Helvetica, meaning Swiss Confederation.”
Usually when you include the dot it’s called TLD or ccTLD (Top Level Domain or Country Code Top Level Domain). Country codes as in ISO 3166 are without the dot, and written with capital letters, and they predate the internet, first published in 1974. The tlds were based on these codes.
There are some minor differences, e.g United States Minor Outlying Islands (UM) and Western Sahara (EH) have a country code, but no tlds were implemented.
Edit: In the article it’s correctly written as
CH