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We report the first observation of the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}(1\mathrm{S},2\mathrm{S})\ensuremath{\eta}$ at $\sqrt{s}=10.866\text{ }\text{ }\mathrm{GeV}$, with significance exceeding $10\ensuremath{\sigma}$ for both processes. The measured Born cross sections are $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}(2\mathrm{S})\ensuremath{\eta})=2.07\ifmmode\pm\else\textpm\fi{}0.21\ifmmode\pm\else\textpm\fi{}0.19\text{ }\text{ }\mathrm{pb}$, and $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}(1\mathrm{S})\ensuremath{\eta})=0.42\ifmmode\pm\else\textpm\fi{}0.08\ifmmode\pm\else\textpm\fi{}0.04\text{ }\text{ }\mathrm{pb}$. We also set the upper limit on the cross section of the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}(1\mathrm{S}){\ensuremath{\eta}}^{\ensuremath{'}}$ to be $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}(1\mathrm{S}){\ensuremath{\eta}}^{\ensuremath{'}})<0.037\text{ …