Swedish nickname

In a sense, all names are two syllables (this is more or less a fact around the world) - one syllable names get lengthened, longer ones get shortened. John > Johnny, Elizabeth > Lizzie. (There are exceptions of course, such as Liz, Beth and so on.)

This is done in a few different ways in Sweden depending on which generation you belong to, but a common “traditional” one is to shorten the first syllable and add an -e suffix to a male name:

Tobias > Tobbe
Karl > Kalle
Jan > Janne
Fredrik > Fredde
Nicklas > Nicke
Filip > Fille

and so on

Jonas > Jonne, but more commonly Jonte, which also works for John, Johan and Johannes (actually three variations of the same name).

There’s a variation to this theme where the phonetics don’t match up:

Gustav > Gurra
Bertil > Berra

Female nicknames work somewhat similarly, mostly with an -i or -a ending instead:

Susanne > Sussi
Cecilia > Cissi
Maria > Mia
Karin > Kajsa (not quite sure how that works , actually)
Sofia > Fia
Annika > Anki (also works for Anna-Karin)
Katrin > Katti/Kattis

Generally, the diminutive/endearing ending in Swedish is the -is seen in Kattis, but it’s usually not applicable to human names. My cat’s name is Tennessee, and calling her Tennis works fine for everyone involved, but adding -is to an adult’s name would mostly be perceived as weirdly infantilizing, except in an established form such as Kattis.

One of my favourite, and very Swedish, ways to make a nickname is to add -son to a name, usually done in a humorous way and not too often with human names: my sister’s dog would be called Melkerson (from Melker), and there’s a hummus bar in my hometown of Malmö called Hummusson, a most excellent name.