thanksgiving (n.)

Old English giefan (West Saxon) "to give, bestow, deliver to another; allot, grant; commit, devote, entrust," class V strong verb (past tense geaf, past participle giefen), from Proto-Germanic *geban (source also of Old Frisian jeva, Middle Dutch gheven, Dutch geven, Old High German geban, German geben, Gothic giban), from PIE root *ghabh- "to give or receive." It became yiven in Middle English, but changed to guttural "g" by influence of Old Norse gefa "to give," Old Danish givæ.

Meaning "to yield to pressure" is from 1570s. Give in "yield" is from 1610s; give out is mid-14c. as "publish, announce;" meaning "run out, break down" is from 1520s. Give up "surrender, resign, quit" is mid-12c. To give (someone) a cold seems to reflect the old belief that one could be cured of disease by deliberately infecting others. What gives? "what is happening?" is attested from 1940. To not give a (some thing regarded as trivial and valueless) is from c. 1300 (early examples were a straw, a grass, a mite).

mid-13c., plural of thank (n.) "expression of gratitude; kind feeling for another after a benefit received or service done," from Old English þanc, þonc in its secondary sense of "grateful thought, good will, gratitude." This is from the same Proto-Germanic root as thank (v.).

In prehistoric times the Germanic noun seems to have expanded from "a thinking of, a remembering" to also mean "remember fondly, think of with gratitude." Compare Old Saxon thank, Old Frisian thank, Old Norse þökk, Dutch dank, German Dank.

The Old English noun chiefly meant "thought, reflection, sentiment; mind, will, purpose," also "grace, mercy, pardon; pleasure, satisfaction," all now obsolete. The noun is used now exclusively in the plural.

Thanks as a common expression or acknowledgment (1580s) is short for I give you thanks, etc.; often with extensions, such as thanks a lot (1908). The form thanx is attested by 1888 as an illiterate spelling, by 1894 as a commercial or informal spelling.

Thanx. That's one way to spell thanks. We are going to close our store from 11 o'clock to 2 oclock Thursday in order to have a short spell of thanx ourselves. [ad for The Mudge Mercantile Company, Eskridge (Kansas) Star, Thu., Nov. 26, 1896]