before 900;Middle Englishthirsten (v.), Old Englishthyrstan, derivative of thurst (noun); cognate with Dutchdorst,GermanDurst,Old Norsethorsti,Gothicthaurstei; noun has -i- from the v. or from thirsty; see toast1
O.E. þurst, from W.Gmc. *thurstus (cf. O.S. thurst, Fris. torst, Du. dorst, O.H.G., Ger. durst), from P.Gmc. *thurs-, from PIE base *ters- "dry" (see terrain). Fig. sense of "vehement desire" is attested from c.1200. The verb is O.E. þyrstan; the fig. sense of the verb was present in O.E. Thirsty is O.E. þurstig.