kaiser

The word 'kaiser' entered English directly from German, where it was the title for emperor. The German term itself evolved from the Latin imperial title 'Caesar', originally the family name of Gaius Julius Caesar. After his death, 'Caesar' became a title for Roman emperors and was adopted by later Germanic peoples. Through the High German consonant shift, the Latin 'c' in 'Caesar' became a 'k', leading to the Old High German form 'keisar' and eventually the modern German 'Kaiser'. Thus, the English word 'kaiser' carries the historical weight of the Roman imperial tradition as filtered through Germanic language and culture.

This is a loanword adopted as a single, unsegmentable unit into English from German. Its internal structure is not productively analyzed using English morphemes.