Eelco's typical online handle is "niksnut", which obviously means "nix nut" but also "good for nothing" :).

It also means nothing in English, though that's somewhat obscure from my perspective. (Looking it up, it sounds like English borrowed it from German a while back.)

In English I think it's most often used as a verb that means basically to cancel. Like, "We're running out of time, we should nix feature X."

Similarly in English. I think "nix", like "git", is a self-deprecating name. It's a play on both "nix" -- to cancel or to not exist, and "nix" as the suffix for Li- and U-.