The tortuous history of the word ‘flan’ (false friend alert!).
The Romans managed to domesticate fowl on a large enough scale for eggs to become readily available as a cheap source of protein. One of the dishes that the Romans exported around Europe was an open pastry filled with egg and other ingredients – either sweet or savoury. It was the centrality of egg that gave rise to the confusion between the two branches of meanings for ‘flan’ that exist in European languages.
The centrality of egg may have led to the confusion, but the word ‘flan’ is deeply rooted in Indo-European language; cognates include Greek platus (= flat, broad), Spanish llano, chato, English ‘flat’, Frankish flado and Dutch vlade (= custard) and vla (= pancake).
The Franks took their flat cakes called flados with them when they invaded Gaul and these eventually became flaons in Old French. In the Middle Ages English adopted the French term – transformed into ‘flawn’ – to refer to a flat cake, a pancake11 or a kind of custard10 or cheesecake. ‘Flan’ entered English from French in the 19th Century referring to an ‘open tart’, typically round and containing fruit. Today in Britain a flan can also be a quiche (i.e. a savoury open tart). So, for example, a quiche Lorraine could be described as an egg-and-bacon flan. Obviously, in British English it would make little sense to describe someone as “shaking like a flan”; we say “to tremble/shake like a leaf” (which makes slightly more sense).
Modern French uses ‘flan’ for an open tart containing fruit. The French term for set custard for dessert is crème caramel, a term also used in British English. In the UK we also use the terms ‘caramel custard’ (when it’s more viscous) and ‘baked custard’ (when is more solid). In American English crème caramel is usually called ‘flan’ under the influence of Spanish and Italian speakers. Crème caramel was introduced into Spain by the Moors. Catalan avoids the problem by calling crème caramel ‘flam’. Catalan flam should not be confused with flaons: cheese-based cakes traditionally eaten at Easter in the Catalan-speaking areas of Spain, whose name derives from the Old French flaon. Savoury flaons are essentially flans in the British sense.
 to manage to – be able to
 fowl – farm birds (such as chickens)
 large enough – sufficient
 source of – way to get
 pastry – mixture of flour, butter and water used to make the solid bases for cakes, quiches, etc.
 to give rise to (give-gave-given) – (in this case) cause
 branch – (in this case) separate evolution
 to be deeply rooted – have ancient origins
 broad – wide
 custard – a viscous yellow dessert made of egg, milk and sugar
 pancake – crêpe
 Gaul – ancient France
 eventually – (false friend) finally, in the end
 kind (n.) – type, sort
 leaf (plural ‘leaves’) – piece of foliage
 slightly – a little
 set – congealed , become semi-solid (like jelly)
 dessert – sweet, pudding, the last part of a meal
 to avoid – get round, not have
 the singular form is flaó
 at Easter – during Holy Week