Where does “Japanesish” come from?

Japanesish (English) comes from English ish, from English -ish, from Middle English -ish, from Old English -isċ, from Proto-West Germanic -isk, from Proto-Germanic -iskaz, from Proto-Indo-European -iskos — Characteristic of, typical of, pertaining to.

Ancestry of “Japanesish”, step by step

Japanesish traces back through two separate lines of ancestry.

via English ish

StepLanguageWordMeaning
1EnglishishPronunciation spelling of is; somewhat,...
2English-ishTypical of, similar to, being like; Somewhat,...
3Middle English-ishAlternative form of -yssh
4Old English-isċ-ish
5Proto-West Germanic-iskCreates adjectives from nouns
6Proto-Germanic-iskazForms adjectives from nouns with the sense of...
7Proto-Indo-European-iskosCharacteristic of, typical of, pertaining to

via English Japanese

StepLanguageWordMeaning
1EnglishJapaneseOf, relating to, or derived from Japan, its...
2EnglishJapanA hard black enamel varnish containing asphalt
3DutchJapan
4MalayJepangJapanese
5Hokkien日本Japan; Japanese; Japan
6Middle Chinese日本Land of the Rising Sun
Every word from Proto-Indo-European -iskosEvery word from English -ishEvery word from Proto-Germanic -iskaz