English
fishscale
From fish + scale.
Proto-Indo-European *piskós
Proto-Germanic *fiskaz
Proto-West Germanic *fisk
Old English fisċ
Middle English fisch ‘an animal that inhabits the water or the meat…’
English fish
Proto-Indo-European *skend- ‘to jump up, ascend’
Proto-Indo-European *(s)kn̥d-sleh₂
Proto-Italic *skand-slā
Latin scāla ‘ladder; stairs’
Middle English scale ‘ladder’
English scale
The story
The use for sense 2 is from its appearance as shiny yellowish flakes resembling the scales of a fish, as opposed to dull white powder.
Today it means
noun The scale of a fish.
Language periods are conventional ranges, not dates for this word.
Etymograph / fishscale