You can tell it's _not_ Cymraeg because of the "j"s.
Despite Jones being the stereotypical name for people in Wales, the old Welsh language, Cymraeg, doesn't have a J, nor have Z, K, V, X (IIRC). Jones is an English loanword, brought over apparently with the Norman conquest (though derived from Hebrew).
The modern language of Wales is of course British English with a ~100% use rate; Cymraeg still has an approx 8% (but falling) of the population who say when surveyed that they can speak it fluently, however.
Off-topic, but I think that traditionally, the longest official word in German was "Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz", the name for a law about testing and labeling of beef, now repealed. This word (63 letters) was of course not in everyday use by most people, but it was actually in the law.
