Where does “hirnrissig” come from?

hirnrissig (German) comes from German rissig, from German -ig, from German -jährig, from German Jahr, from Middle High German jār, from Old High German jār, from Proto-West Germanic jār, from Proto-Germanic jērą — year.

hirnrissig (German): stupid, idiotic, brainless

Definitions

  1. stupid, idiotic, brainless

Ancestry of “hirnrissig”, step by step

hirnrissig traces back through two separate lines of ancestry.

via German rissig

StepLanguageWordMeaning
1Germanrissigcracked having cracks
2German-ig-y; forms adjectives from nouns; forms adjectives...
3German-jährigyears old; years lasting
4GermanJahryear
5Middle High Germanjāryear
6Old High Germanjāryear
7Proto-West Germanicjāryear
8Proto-Germanicjērąyear; name of the J-rune
9Proto-Indo-Europeanyeh₁r-year

via German Hirn

StepLanguageWordMeaning
1GermanHirnbrain
2Middle High Germanhirne
3Old High Germanhirnibrain
4Proto-West Germanic*hirʀnībrain
Every word from Proto-Indo-European yeh₁r-Every word from German -igEvery word from Proto-Germanic jērą