Webster's Revised Unabridged Dictionary · 1913

thank

thank (thank) , noun

[Anglo-Saxon þanc, þonc, thanks, favor, thought; akin to Old Saxon thank favor, pleasure, thanks, Dutch & German dank thanks, Icelandic þokk, Danish tak, Swedish tack, Gothic þagks thanks; -- originally, a thought, a thinking. See Think.]

A expression of gratitude; an acknowledgment expressive of a sense of favor or kindness received; obligation, claim, or desert, or gratitude; -- now generally used in the plural.
This ceremonial thanks. — Massinger
If ye do good to them which do good to you, what thank have ye? for sinners also do even the same. — Luke vi. 33
What great thank, then, if any man, reputed wise and constant, will neither do, nor permit others under his charge to do, that which he approves not, especially in matter of sin? — Milton
Thanks, thanks to thee, most worthy friend, For the lesson thou hast taught. — Longfellow
Full sooth is said that love ne lordship, Will not, his thanks, have no fellowship. — Chaucer

Thank , transitive verb

[Anglo-Saxon þancian. See Thank, n.]

To express gratitude to (anyone) for a favor; to make acknowledgments to (anyone) for kindness bestowed; -- used also ironically for blame.
“Graunt mercy, lord, that thank I you,” quod she. — Chaucer
I thank thee for thine honest care. — Shakespeare
Weigh the danger with the doubtful bliss, And thank yourself if aught should fall amiss. — Dryden