Entries linking to thousandth
"10 times one hundred; the number which is ten times one hundred; a symbol representing this number;" Old English þusend, from Proto-Germanic *thusundi (source also of Old Frisian thusend, Dutch duizend, Old High German dusunt, German tausend, Old Norse þusund, Gothic þusundi).
Related to words in Balto-Slavic (Lithuanian tūkstantis, Old Church Slavonic tysashta, Polish tysiąc, Russian tysiacha, Czech tisic), and probably ultimately a compound with indefinite meaning "great multitude, several hundred," literally "swollen-hundred," with first element from PIE root *teue- "to swell," second element from PIE root *dekm- "ten."
Used to translate Greek khilias, Latin mille, hence the refinement into the precise modern meaning. There was no general Indo-European word for "thousand." Slang shortening thou first recorded 1867. Thousand island dressing (1916) presumably is named for the region of New York on the St. Lawrence River.
word-forming element making ordinal numbers (fourth, tenth, etc.), Old English -ða, from Proto-Germanic *-tha- (cognates: Gothic -da, -ta, Old High German -do, -to, Old Norse -di, -ti), from PIE *-to-, also *-eto-, *-oto-, suffix forming adjectives "marking the accomplishment of the notion of the base" [Watkins].
Cognate with Sanskrit thah, Greek -tos, Latin -tus; Sanskrit ta-, Lithuanian and Old Church Slavonic to, Greek to "the," Latin talis "such;" Greek tēlikos "so old, of such an age," Old Church Slavonic toli "so, to such a degree," toliku "so much," Russian toliko "only;" also see -ed.