bywater
(ˈbaɪwɔːtə(r))
[f. by- B 5 + water n. 20.]
A diamond of inferior water, yellowish in colour; also attrib.
| 1878 [see off colour 2]. 1895 Westm. Gaz. 1 Oct. 2/1, I..woke up to consider two fresh lots of treasure, ‘whites’ and ‘by-waters’, so termed from their colour. 1916 F. B. Wade Diamonds 25 Yellows, or by-waters. |