Here comes a lot of unsought, but I hope welcome information:


Indo-European Roots


ENTRY:
ter-1
DEFINITION:
To rub, turn; with some derivatives referring to twisting, boring, drilling, and piercing;
and others referring to the rubbing of cereal grain to remove the husks, and thence to
the process of threshing either by the trampling of oxen or by flailing with flails. Oldest
form *ter1-, with variant *tre1-, contracted to *tr-.
Derivatives include trite, detriment, thrash, trauma, and truant.
I. Full-grade form *ter()-. 1a. trite, triturate; attrition, contrite, detriment, from
Latin terere (past participle trtus), to rub away, thresh, tread, wear out; b. teredo,
from Greek terdn, a kind of biting worm. 2. Suffixed form *ter-et-. terete, from
Latin teres (stem teret-), rounded, smooth. 3. Suffixed form *ter-sko-. a. thrash,
thresh, from Old English therscan, to thresh; b. threshold, from Old English
therscold, threscold, sill of a door (over which one treads; second element obscure).
Both a and b from Germanic *therskan, *threskan, to thresh, tread.
II. O-grade form *tor()-. 1. toreutics, from Greek toreus, a boring tool. 2.
Suffixed form *tor()-mo-, hole. derma2, from Old High German darm, gut, from
Germanic *tharma-. 3. Suffixed form *tor()-no-. turn; attorn, attorney, contour,
detour, return, from Greek tornos, tool for drawing a circle, circle, lathe.
III. Zero-grade form *tr-. drill1, from Middle Dutch drillen, to drill, from Germanic
*thr-.
IV. Variant form *tr- (< *tre-). 1. throw, from Old English thrwan, to turn,
twist, from Germanic *thrw-. 2. Suffixed form *tr-tu-. thread, from Old English thr
d, thread, from Germanic *thrdu-, twisted yarn. 3. Suffixed form *tr-m (<
*tre- or *t-). monotreme, trematode, from Greek trma, perforation. 4. Suffixed
form *tr-ti- (< *tre- or *t-). atresia, from Greek trsis, perforation.
V. Extended form *tr- (< *tri-). 1. Probably suffixed form *tr-n-. septentrion,
from Latin tri, plow ox. 2. Suffixed form *tr-dhlo-. tribulation, from Latin trbulum,
a threshing sledge.
VI. Various extended forms 1. Forms *tr-, *trau-. trauma, from Greek trauma,
hurt, wound. 2. Form *trb-. diatribe, triboelectricity, tribology, trypsin, from Greek
trbein, to rub, thresh, pound, wear out. 3. Form *trg-, *trag-. a. trogon, trout, from
Greek trgein, to gnaw; b. dredge2, from Greek tragma, sweetmeat. 4. Form
*trup-. trepan1; trypanosome, from Greek trup, hole. 5. Possible form *trg-.
truant, from Old French truant, beggar. (Pokorny 3. ter- 1071.)


From another site, toreutics is the study of art work in metal.