'Thousand' is Proto-Germanic for 'swelling hundred' — a uniquely Germanic compound with no Latin or Greek cognate.
The cardinal number equivalent to ten times one hundred; the number 1,000.
From Old English 'þūsend,' from Proto-Germanic *þūsundī, a compound whose exact etymology is debated. The most widely accepted analysis derives it from PIE *tuHs-ḱm̥t-ih₂, meaning 'swelling hundred' or 'strong hundred' (from *teuH- 'to swell, to be strong' + *ḱm̥tóm 'hundred'). This would make 'thousand' literally a 'fat hundred
Unlike most basic English numerals, 'thousand' has no cognate outside the Germanic language family — Latin used 'mīlle,' Greek used 'khī́lioi,' and Sanskrit used 'sahásra,' all from different roots. The word 'thousand' appears to be a uniquely Germanic coinage, literally meaning 'swelling hundred' or 'strong hundred.'