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Carlo Beenakker
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The suffix $-oid$ means the same as "quasi", so resembling, "like". A groupoid is a quasi-group, like a group.

From the "early use" database I find:

250 BC: conchoid
200 BC: cissoid
1685: cochleoid
1830: epicycloid
1844: centroid
1872: geoid, gyroid
1881: prismatoid
1891: cuboid

Carlo Beenakker
  • 188.2k
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  • 651