"Thanksgiving," what does it mean? One way to learn about a word is to use the "OED," the Oxford English Dictionary. This is the primary in depth place to learn about a word, its meanings, origins, history of usage... For example, below is just a small part of the OED entry for the word Thanksgiving:
Pronunciation: /ˈθæŋksˌɡɪvɪŋ/ Etymology: < thanks, plural of thank n. + giving n.
a. The giving of thanks; the expression of thankfulness or gratitude; esp. the act of giving thanks to God.1533 Tyndale Souper of Lorde E iv b, One or other Psalme or prayer of thankes giuyng in the mother tongue.
1539 Bible (Great) 1 Tim. iv. 4 For all the creatures of God are good, and nothing to be refused, yf it be receaued with thankesgeuynge.
1562 N. Winȝet Certain Tractates (1888) I. 29 Gyf sic zeirlie memorial in blythnes and thankisgeifing wes haldin.
1598 Shakespeare Love's Labour's Lost ii. i. 193, I cannot stay thankes-giuing.
1658 Whole Duty of Man v. §8 The fifth part of prayer is thanksgiving; that is, the praising and blessing God for all his mercies.
1842 M. R. Mitford in A. G. L'Estrange Life M. R. Mitford (1870) III. ix. 159 Think how full of thanksgiving were my prayers last night.