Louis was a Top 100 name in the U.S. from 1880–1959, with a peak of #18 in 1882. It gradually began falling in popularity during the 1920s, and fell out of the Top 50 in 1942. In 2009, it reached its lowest rank of #353. In 2016, it was #289.
Louis is the French form of Ludovicus, which in turn is the Latinized form of the German Ludwig. Its ultimate origin is the Old Germanic Chlodovech, which is composed of the elements hlud (famous) and wig (battle, war).
Louisa likewise has seen much more popular days, though it was never close to as popular as Louis. Its highest rank was #119 in 1881, and its final year in the Top 1000 was 1969, when it was #954. It only re-entered in 2014, at #971. By 2016, it was #825.
The French and English variant form Louise has historically been more popular than Louisa. It was in the Top 100 from 1880–1948, with the highest rank of #17, from 1912–14. Like its counterparts, it gradually began sinking, and fell out of the Top 1000 in 1988. It re-entered in 1990, fell out again in 1992, and had another re-entrance in 2016, at #895.
Louise is much more popular in France (#1) and Belgium (#2). It’s also fairly popular in Norway (#75), Switzerland (#73), and The Netherlands (#101). Louis also enjoys more popularity outside the U.S. It’s #1 in Belgium, #4 in France, #12 in Switzerland, #59 in Australia, #71 in England and Wales, and #82 in New Zealand.
Other forms of these names include:
1. Ludwik is Polish.
2. Ludwig is German.
3. Ludvig is Scandinavian, with the nickname Ludde.
4. Ludoviko is Esperanto, with the nickname Lučjo.
5. Lodewijk is Dutch, with nicknames including Ludo and Lowie.
6. Loïc is Breton and French.
7. Ludovico is Italian.
8. Lodovico is an Italian variant.
9. Ludis is Latvian.
10. Ludvigs is also Latvian.
11. Liudvikas is Lithuanian.
12. Lluís is Catalan.
13. Luis is Spanish, with the nickname Lucho. The variant Luís is Portuguese.
14. Lúðvík is Icelandic. The alternate form Ludvík is Czech, with the nickname Luděk.
15. Loís is Occitan. The variant Lois is Galician.
16. Ludovic is French.
17. Luigi is Italian, with nicknames including Gino and Luigino.
18. Luiz is Brazilian–Portuguese.
19. Lodosis is Aragonese.
20. Loeiz is Breton.
21. Loudovikos is a rare Greek form.
22. Loys is Gascon.
23. Lûíse is Greenlandic.
24. Lujo is Croatian.
25. Luui is Greenlandic.
26. Lüwi is Alsatian.
27. Koldobika is Basque, with the nickname Koldo.
28. Alajos is Hungarian.
29. Alojz is Slovak, Slovenian, and Croatian. The Slovenian nickname is Lojze.
30. Alojzij is Slovenian.
31. Alojzije is Croatian.
32. Aloysius is the Latinized form of Aloys, an archaic Occitan form of Louis.
33. Alois is German and Czech.
34. Alojzy is Polish.
35. Aloisio is Italian.
36. Alvise is Venetian.
37. Aloísio is Portuguese.
38. Alaois is Irish.
39. Aloxi is Basque.
40. Rewi is Maori.
41. Ruihi is also Maori.
42. Lajos is Hungarian.
1. Luisa is Spanish, Italian, Romanian, Czech, Slovak, German, Dutch, and Croatian. The variant Luísa is Portuguese.
2. Luiza is Russian, Romanian, Polish, and Brazilian–Portuguese.
3. Lujza is Hungarian and Slovak.
4. Louiza is Greek.
5. Liudvika is Lithuanian.
6. Loviise is Estonian.
7. Lovise is Norwegian and Danish.
8. Lovisa is Swedish.
9. Lluïsa is Catalan.
10. Ludwika is Polish.
11. Loviisa is Finnish.
12. Ludovica is Italian.
13. Luigia is also Italian, with nicknames including Gina and Luigina.
14. Luise is German.
15. Alojzia is Slovak.
16. Aloiziya is Bulgarian.
17. Alojzija is Slovenian and Croatian.
18. Lavīze is a rare Latvian form.
19. Loeiza is Breton.
20. Loïsa is Occitan.
21. Loisa is Galician.
22. Ludovique is a rare French form.
23. Luīze is Latvian.
24. Lüwiss is Alsatian.
25. Ruiha is Maori.