Where does “toadstool disease” come from?

toadstool disease (English) comes from English disease, from Middle English disese, from Anglo-Norman desese, from Old French desaise, from Old French eise, from Latin adiacēns, from Latin adiaceo, from Latin ad- — in.

Ancestry of “toadstool disease”, step by step

toadstool disease traces back through two separate lines of ancestry.

via English disease

StepLanguageWordMeaning
1EnglishdiseaseAn abnormal condition of a human, animal or plant...
2Middle Englishdisese
3Anglo-Normandesese
4Old Frenchdesaisedisease; deformity; melancholy
5Old Frencheiseease
6Latinadiacēnsadjacent, adjoining, neighbouring
7LatinadiaceoI lie beside, at, near or next to; am adjacent...
8Latinad-to; usually prefixed to verbs, in which cases it...
9Latinīn-un-, non-, not
10Latinînin, at, on, upon, from (space)
11Latinenlookǃ beholdǃ; reallyǃ?; come onǃ
12Proto-Italicenin
13Proto-Indo-Europeanh₁énin

via English toadstool

StepLanguageWordMeaning
1EnglishtoadstoolAny inedible or poisonous mushroom, especially an...
2EnglishstoolA seat, especially for one person and without...
3Middle Englishstool
4Old Englishstōlchair, seat, throne
5Proto-West Germanic*stōlstool, chair
6Proto-Germanicstōlazstool; throne; chair
7Proto-Indo-Europeanstoh₂losframe, rack, stand
8Proto-Indo-Europeansteh₂-to stand
Every word from Proto-Indo-European h₁én