Lewis & Short

quămobrem (or quăm ob rem), adv. [quam-ob-rem] (class.).

  1. I. Interrog., for what reason? on what account? wherefore? why? Am. Scelestissumum te arbitror. So. Nam quamobrem? Am. Quia, etc., Plaut. Am. 2, 1, 2: quem ad finem? … quamobrem? quam ob causam? Cic. Verr. 2, 5, 29, § 75; id. Fin. 1, 5, 15.
    In indirect questions: cum quaereret quam ob rem Ariovistus non decertaret. Caes. B. G. 1, 50.
  2. II. Rel., from which cause or reason, wherefore, why: hoc est homini, quamobrem vitam amet, Plaut. Ps. 5, 1, 11; id. Most. 2, 1, 66; id. Aul. 4, 10, 6: multae sunt causae, quamobrem cupio abducere, Ter. Eun. 1, 2, 65; Cic. Fam. 3, 10, 1: verum illud est, quamobrem haec commemorarim, id. Verr. 2, 4, 60, § 135: si res reperietur, quam obrem videantur, id. Rosc. Am. 3, 8; id. Caecin. 33, 96.
      1. 2. At the beginning of a sentence, as a particle of transition, on which account, for which cause, wherefore: quamobrem quaeso a vobis, Asiatici testes, Cic. Fl. 27, 65: quamobrem quoniam, etc. … utar eā clausulā, etc., id. Fam. 2, 4, 2; 10, 10, 1.