Where does “US-Amerikanerin” come from?

US-Amerikanerin (German) comes from German US-Amerikaner, from German Amerikaner, from German -er, from Old High German -āri, from Proto-West Germanic -ārī, from Proto-Germanic -ārijaz, from Latin -ārius, from Proto-Italic *-āzios — Forms relational adjectives to nouns (and rarely numerals).

Ancestry of “US-Amerikanerin”, step by step

StepLanguageWordMeaning
1GermanUS-AmerikanerAmerican, U.S. American
2GermanAmerikanerAmerican; US-American; A round cakelike pastry of...
3German-erForms agent nouns etc. from verbs, suffixed to...
4Old High German-āriused to form agent nouns
5Proto-West Germanic-ārī-er
6Proto-Germanic-ārijaz-er
7Latin-āriuser
8Proto-Italic*-āziosForms relational adjectives to nouns (and rarely numerals)
Every word from Proto-Italic *-āzios