The name ‘Indian summer’ (late 18th century) reflected the fact that to the Europeans living in the New World, this was a newly-discovered local phenomenon. But similar phenomena were already known in the Old World by various names.
Greek ‘δορυϕόρος’ (‘doruphόros’) meant ‘spearman’; in French, ‘doryphore’ denotes the Colorado beetle and the German occupying forces during WWII; in English, it denotes a pedantic and annoyingly persistent critic.
19th century—The adverb ‘hands down’ originated in horse racing: a jockey who is winning comfortably is able to lower his hands and relax his hold on the reins.
Etymologically, ‘Shrovetide’ denotes the period during which it was customary to attend confession in preparation for Lent—but this period was also marked by feasting before the Lenten fast.
French—from the noun use of the Latin adjective ‘natalis’ (from Christian-Latin ‘natalis dies’, ‘day of birth’), denoting the festival of the nativity of Christ
in full ‘Quasimodo Sunday’: the Sunday after Easter—from the opening words of the Latin introit for that day, ‘quasimodo geniti infantes’, ‘as newborn babies’
Swiss-French ‘crestin’ (= ‘Christian’): in certain valleys of the Alps, a mentally deficient, deformed person suffering from a congenital thyroid deficiency