ferdeko

Say the false seam out loud, because it is a good one. Fero is iron. Deko would be a ten, a set of ten, from dek. So ferdeko ought to be an iron ten, which is not a thing, and a learner who has been trained by fulmotondro and taglibro to split compounds at the seam will split this one and get nonsense. The nonsense is the useful part: it tells you immediately that the seam is not there, because Esperanto compounds mean the sum of their pieces and this one does not.

Where it really comes from. German Verdeck, the deck of a ship, from decken, to cover. Esperanto took the German word whole and respelled it, Verdeck to ferdek-, because v before a consonant and the German -eck do not survive the transfer intact. So the fer- at the front is the German prefix ver-, which is not iron and not anything else in Esperanto, and the -dek- is cover, which is not ten. Both halves are decoys, produced by a single borrowing. A deck is what covers the hull, which is what the German has been saying all along.

This is the class of word to be suspicious of. Esperanto's roots come from five or six European languages, and when a borrowed root happens to land on top of two existing Esperanto roots you get a word that looks built and is not. Ferdeko is the cleanest example in this chapter; perturbi, a few ranks later, is the other one. The defence is simple and cheap: when the decomposition gives you nonsense, stop decomposing and look the word up. Compounds in Esperanto are transparent by design, so an opaque result means you have guessed wrong about what kind of word you are holding.

On board. Sur la ferdeko is on deck, sub la ferdeko below decks. Duferdeka and triferdeka are two-decked and three-decked, and they are the standard way to describe a vessel's size in older Esperanto sea writing. Ferdekano would be somebody who lives on deck; the ordinary crew word is maristo. And a card deck is not ferdeko at all: that is kartaro, built with the collective -ar- exactly as you would expect.