Where does “piecewise smooth” come from?

piecewise smooth (English) comes from English piecewise, from English piece, from Middle English pece, from Old French piece, from Vulgar Latin pettia, from Latin pettia, from Gaulish pettyā, from Proto-Celtic kʷezdis — piece, portion.

piecewise smooth (English): to a sum of finitely many parts, each of which is smooth; often said of curves and surfaces

Definitions

  1. to a sum of finitely many parts, each of which is smooth; often said of curves and surfaces

Ancestry of “piecewise smooth”, step by step

piecewise smooth traces back through two separate lines of ancestry.

via English piecewise

StepLanguageWordMeaning
1EnglishpiecewiseIn terms or by means of pieces; a piece at a...
2EnglishpieceA part of a larger whole, usually in such a form...
3Middle Englishpecepiece; morsel; bit
4Old Frenchpiecepiece, bit, part; circa 1170, Chrétien de Troyes
5Vulgar Latinpettiapiece, portion
6Latinpettiapiece, portion
7Gaulishpettyā
8Proto-Celtickʷezdispiece, portion

via English smooth

StepLanguageWordMeaning
1EnglishsmoothHaving a texture that lacks friction. Not rough;...
2Middle Englishsmethesmooth not rough
3Old Englishsmōþsmooth, serene, calm, unruffled
4Proto-Germanicsmanþizflat, smooth, soft
Every word from Proto-Celtic kʷezdis