How to pronounce Celtics?

Question

In ESPN videos (1, 2), Boston Celtics was pronounced as /sel-tik/, but the dictionary says both /kel-tik/ and /sel-tik/ are acceptable pronunciations and clicking the sound icon on the dictionary website gives /kel-tik/.

Questions:

• How did this word come to have two different but acceptable pronunciations?

• Which pronunciation is more common? Does this depend on the country or area you live in?

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Edit:

This is what I have found about the pronunciation of celts. To make it short, the pronunciation was originally /k/, but later changed to /s/. Then /k/ went into German, /s/ went into French and both went into English. For a long time it remained /s/ in English following the French convention, but recently /k/ gained ground again. However, /s/ is the most recognised form in names of sports teams.

This reveals some history about the pronunciation but still doesn't answer how this word is pronounced in modern English by native speakers. It gives me the illusion that /k/ is more common but /s/ should be used for sports teams. I'm not quite sure if this illusion is false.

Answer 1

The relevant portion of the Wikipedia source you gave is:

The pronunciation with /s/ remained standard throughout the 19th to early 20th century, but /k/ gained ground during the later 20th century.

The Boston Celtics were formed in 1946 (and the Glasgow Celtics, as mentioned in a comment to the question, in 1891).

This was when the common pronunciation was still with /s/.

Although the common pronunciation for the word shifted to /k/ after that, the pronunciation of the team name remained.