I. UNTHANK, noun, obsolete. Old English (Anglo Saxon) unþanc, masc. (The Anglo Saxon letter þ is pronounced "th"); Old Frisian, unthank; Mid. Dutch, ondanc; Mid Low German, undank; Old High German undanch, unthank; M. Swedish, othak; Danish utak; etc.
1. Absence of Gratitude or good-will; unfavorable thought of feeling; ill-will; disfavor; displeasure expressed inaction or words.
Used as such by King Alfred, in "Ores," c. 893; Sal & Sat, c. 1000; c. 1380, Wycliff; c. 1386, Chaucer.
2. In the phrase, to have unthank.
Used, c. 1325, 1380.
3. An act or circumstance causing displeasure or annoyance; an offence or injury.
Used c. 897, King Alfred, "Gregory Past"; c. 1000; c. 1205.
4. In uses denoting disinclination, reluctance, or involuntariness.
5. In the genitive, used adverbally -- unwillingness, without one's consent.
Used, c. 960, Laws Edgar; 1066, O. E. Chronicle.
6. More frequently, with possessive adjective.
Used, King Alfred "Ores," c. 893; 1100, O. E. Chronicle.
II. UNTHANK, verb, transitive. To unsay or recall one's thanks to.
1. Unthanked, ppl, adj.
2. Unthankful, adj. (Cf. Old English, unþancful)
a. Not earning thanks or gratitude; unacceptable; thankless. Also inadequate, insufficient
b. Not rendering thanks; not feeling or exhibiting gratitude.
c. Characterized by ingratitude.
3. Unthankfulness; ingratitude.
4. Unthankfully, adv.; Ungratefully
From "A dictionary of English and Welsh Surnames"; Bardsley, 1901. We find:
Unthank, Onthank. -- Local; "of Unthank"
From "British Family Names"; Barber, 1903
UNTHANK. A local name. Cumberland and Northumberland.
From "History and Antiquities of North durham"; Raine, 1852.
"Unthank is a genuine Saxon word, terra ingrata, barren, making no return. the name, which is common in the North, is always found in connection with such unproductive situtations."
Turning an eye to more modern sources we find....
From "Webster's Revised Unabridged Dictionary". MICRA, Inc. 1996, 1998, 23 Nov. 2009.
Un*thank"\, n. [AS. unpank. See Un- not, Thank.] No thanks; ill will; misfortune. [Obs.]
Unthank come on his head that bound him so. --Chaucer.
From "Name Orgin Research - The Internet Surname Database" www.surnamedb.com 1980 - 2009
"Recorded as Unthank and sometimes Onthank, this is a most unusual and rare English surname. It has nothing to do with not thanking somebody, but is locational. It originates from three villages called Unthank, two in Cumbria, the other in the neighbouring county of Northumberland, on the Scottish border. According to the Oxford Directory of English Place Names, the place and hence the surname derives from a pre 7th century Olde English word "unpance" which means literally "without leave," and described an area of land which was occupied unlawfully. If this was the case it seems strange that the powerful landowners of the time did not trouble themselves to remove these interlopers, before the places became established, but clearly they did not. This suggests that since the villages were in an area of continual dispute between the English and the Scots, it may have suited the overlords perhaps the famous Percy family, to leave well alone, particularly if the villagers gave allegiance to them. All three places were first recorded about the year 1200, just about in time for four hundred years of strife, before the accession of James V1 of Scotland to the throne of England in 1603. After that with unification, peace gradually returned to the area. The first recording is probably that of William de Unthanc in the History of Northumberland in 1233, with Richard de Unthank in the Hundred Rolls of Landowners of Cumberland in 1273, and Henry Onthanke who married Margery Maye, in London, in 1577."