from the 16th-century phrase ‘to set cock a hoop’, ‘to set (the) cock on (the) hoop’, apparently meaning ‘to put the cock (= spigot) on a barrel hoop and let the liquor flow prior to a drinking bout’—‘cock’ later equated with the fowl and ‘hoop’ with French ‘huppe’ (tufted crest)
A humorous alteration of ‘au revoir’ after the noun ‘reservoir’, the exclamation ‘au reservoir’ is first recorded in Little Pedlington and the Pedlingtonians (London, 1839), by the English author John Poole (1786-1872).
First attested in 1943, the British-English colloquial phrase ‘to go (all) round the houses’ means ‘to get to the point in a lengthy or roundabout way’, from its literal sense, ‘to take an unnecessarily circuitous route to one’s destination’.
‘yahoo’: rude, noisy or violent person—word invented by Jonathan Swift (1667-1745) as the name of a race of brutish creatures resembling men in Gulliver’s Travels (1726)—came to be applied to the orang-utan
‘dunce’: originally a follower of John Duns Scotus (circa 1265-1308), scholastic theologian; in the 16th century, Scotus’s system was attacked with ridicule by the humanists and the reformers as a farrago of needless entities and useless distinctions
an epithet for William Shakespeare, born at Stratford-upon-Avon, on the River Avon—first used by Ben Jonson in the earliest collected edition (1623) of Shakespeare’s plays—but this use of ‘swan’ for a bard, a poet, is rooted in a tradition going back to antiquity
Italian translation of Latin ‘in pectore’ (‘in the breast’, ‘in the secret of the heart’)—when a pope announces that he has appointed a cardinal whom he reserves ‘in petto’, it means that he will reveal this cardinal’s name later
UK, early 19th century—private property taken from an enemy in war—originally an Anglo-Indian noun, from Hindi ‘lūṭ’, from Sanskrit ‘luṇṭh-‘, ‘to rob’—came to be also used as slang for ‘money’ and to also denote ‘wedding presents’
‘slipshod’: ‘characterised by a lack of care, thought or organisation’—formed after the obsolete noun ‘slip-shoe’ (= ‘a loosely fitting shoe or slipper’); ‘shod’ (meaning ‘wearing shoes’) is the past participle of the verb ‘shoe’
From ‘rīvus’, ‘a stream’, the Latin adjective ‘rīvālis’ (of, or belonging to, a stream) was used as a plural noun, ‘rīvāles’, to denote persons who have to use the same stream, and persons who have the same mistress, competitors in love.