Where does “dropsen” come from?

dropsen (Welsh) comes from Welsh -en, from Proto-Brythonic -enn — Forms abstract derivatives of certain nouns and adjectives.

Ancestry of “dropsen”, step by step

StepLanguageWordMeaning
1Welsh-enUsed to form the singulative of certain words;...
2Proto-Brythonic-ennForms abstract derivatives of certain nouns and adjectives
Every word from Proto-Brythonic -enn →Every word from Welsh -en →