nonchalant: [18] To be nonchalant is etymologically ‘not to get hot under the collar’. The word comes from French nonchalant, an adjective formed with the prefix non- ‘not’ from the present participle of the verb chaloir ‘be concerned’. This goes back ultimately to Latin calēre ‘be hot’ (a relative of English calorie and cauldron). => calorie, cauldron, lukewarm
