by Jove!, (an exclamation used to emphasize an accompanying remark or to express surprise, approval, etc.):
It was a good fight, by Jove!
Origin
1325-75;Middle English < LatinJov- (oblique stem of compound nominative Juppiterfather Jove), akin. to deus god; cognate with GreekZeús (genitive Diós) Zeus
Roman god of the bright sky, late 14c., from Latin Iovis, from PIE *dyeu- "to shine," with derivatives referring to the sky, heavens, a god (see diurnal, and cf. Zeus). In classical Latin, the compound Iuppiter replaced Old Latin Iovis as the god's name.