Sometimes a name's journey is a straight line. Other times, it's a bizarre inter-cultural mash-up of 'Telephone' and 'Hot Potato'. Chlodovech is the latter. It has two forms in modern English, one much more common than the other--can you guess them beforehand?
Chlodovech (kloh-doh-vek) was an Ancient Germanic name, with the pretty awesome meaning of "famous warrior". Now, a lot of people think that Latin is about the oldest language ever, but a) it lasted quite a while, and b) it's a sister language to Ancient Germanic. They co-existed, and passed words & names back & forth as the Romans did their conquering empire thing. Chlodovech was a royal name to the ancient Frankish family, and were so mentioned in ancient Roman writings. The Romans had a tendency to alter names to fit what they thought names should look like (and to eliminate sounds & sound combinations that were too tricky for Latin speakers), and so they wrote Chlodovech as Clodovicus or Ludovicus.
Clodovicus was shortened to Clovis, and is still used today in French and Portuguese.
Ludovicus.....fun times. It spread back into Germanic areas, where people apparently didn't recognize it as Chlodovech (rather understandable), and so altered it again--Ludwig.
In French, Ludovicus was shortened to Louis, and from there, Luigi in Italian, Luis in Spanish, and Lewis/Louis in English. In Occitan (a Latinate language closely related to Catalan), however, an initial vowel was needed, and so Louis became Aloys (ah-loh-ees).
But then! Aloys was imported back into Latin (yup, still around in the RC church). Aloys was lengthened to Aloysius, which then caught on in many languages, including, one day, English.