Hydraulics and pneumatics

The tenth entry is diâmetro do êmbolo, and the noun inside it is a Greek word that English owns without ever using it for machinery. Émbolos was the thing driven in, built on en-, in, and bállein, to throw, and it named a stopper or a plug long before anybody built an engine. Portuguese kept it for the moving part: o êmbolo is the piston in a cylinder, and o êmbolo da seringa is the plunger a nurse pushes down. English sent the same word to the clinic instead. « An embolus » is the clot or the bubble thrown into a vessel, « an embolism » is what it causes, and neither will do in a workshop. For the machine English went shopping in Italy and took « a piston », from pistone, built on a verb meaning to pound. The Greek verb is worth keeping in view, because it also threw « a problem » forward and « a symbol » together, and, through the very prefix of this entry, it threw « an emblem » in. So o êmbolo and « an emblem » are one word twice over, and only one of them moves.