.
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
info. source here
A LITTLE SOMETHIN' 
ok i find this fascinating…i dont have any clue what it means…but it is fascinating…
Word derviations are so fascinating.