Word Origin & History
O.E. þancian "to give thanks," from P.Gmc. *thankojan (cf. O.S. thancon, O.N. þakka, Dan. takke, O.Fris. thankia, M.Du., Ger. danken "to thank"), from *thankoz "thought, gratitude," from PIE base *tong- "to think, feel." For sense evolution, cf. related O.E. noun þanc, þonc,
originally "thought," but by c.1000 "good thoughts, gratitude." The whole group is from the same root as think
(q.v.). In ironical use, "to blame," from 1550s. Thank you is attested from c.1400, short for I thank you. To thank (someone) for nothing is recorded from 1703.