Etymology From Middle English trowen, trouwen, treuwen, treowen, trouen, from Old English trēowan, trīewan (“to trust”) and Old English trūwian (“to trust, confide”), from Proto-Germanic *trewwāną (“to trust”) and Proto-Germanic *trūwāną (“to trust”); both from Proto-Indo-European *drew- (“faithful, true”). Akin to Scots trow, trew (“to believe, trust, confide in, prove”), Dutch trouwen (“to wed, marry”), German trauen (“to trust, marry”), Danish, Norwegian Bokmål and Swedish tro (“to believe, think”), Norwegian Nynorsk tru (“to believe, think”), Icelandic trúa (“to trust, believe, believe in”).
...Sure (he said) my wife shall never know Of this escape, and if she do, I know the worst I trow She can but chide, shall feare of chiding make me to forslow?1567, Arthur Golding: Ovid's Metamorphoses; Bk. 2 lines 527-9
Finding me stick to her still like wax, for my mettle was up as hers was, away she flew with me swifter than ever I went before, or since, I trow.1869, R[ichard] D[oddridge] Blackmore, chapter X, in Lorna Doone: A Romance of Exmoor. […], volume (please specify |volume=I to III), London: Sampson Low, Son, & Marston, […], →OCLC:
2 more examples
"And as their valour, so you trow, defied on aspe'rous voyage cruel harm and sore, so many changing skies their manhood tried, such climes where storm-winds blow and billows roar[.]"1880, Richard Francis Burton, Os Lusíadas, volume I, page 23:
But was the matter allowed to end there? I trow not.1895, Kenneth Graham, The Golden Age, London, page 6:
2
Archaic, Dialectal To have confidence in, or to give credence to.
Etymology From Middle English trowen, trouwen, treuwen, treowen, trouen, from Old English trēowan, trīewan (“to trust”) and Old English trūwian (“to trust, confide”), from Proto-Germanic *trewwāną (“to trust”) and Proto-Germanic *trūwāną (“to trust”); both from Proto-Indo-European *drew- (“faithful, true”). Akin to Scots trow, trew (“to believe, trust, confide in, prove”), Dutch trouwen (“to wed, marry”), German trauen (“to trust, marry”), Danish, Norwegian Bokmål and Swedish tro (“to believe, think”), Norwegian Nynorsk tru (“to believe, think”), Icelandic trúa (“to trust, believe, believe in”).