Welsh and occasionally English, from Aloysius which is ultimately from Old German "famous warrior".
Several spelling variations occur in the 1841 Census of Aberdeenshire for Louis/Lewis [q.v.]. These include Lewas, Lewes, Lewies, Loues, Lues, Luis and Lowis. When searching old records, these spellings should be considered as possible variants. Most or all should be returned by using Soundex searching.
FreeREG lists Aloysius as a Latinised version of Llewellyn [Welsh] or Lewis [Irish] in old documents, and Llewellyn is sometimes Anglicised as Lewis. Search on Aloysi* to cater for Latin endings.
There are examples of at least two men called both Lewis and Ludovick on Parish records in Aberdeenshire. We therefore believe that Lewis/Louis and Ludovic/Ludovick should be considered to be synonyms, in Scotland at least.