lanco

One root, all the way through. Lanc- plus -o, and there is nothing else in there. The word looks as though it might be lan- (wool) with something attached, and it is not; nor is it related to lanĉi, to launch, which is a separate borrowing from English and differs by a hat. This is a plain international root of the sort Esperanto takes whole when the concept is concrete and old.

The register is historical and military, and it is worth being deliberate about that, because English has softened lance into hospitals and tournaments. In Esperanto a lanco is a weapon: the thing a kavaliro carried on horseback, the thing a Roman legionary threw. Read it in a mezepoko passage and it means what it says. The surgical instrument is a lanceto, and the diminutive is doing real work there.

Where it sits among the neighbours. Glavo is a sword, sago is an arrow, pafarko is the bow that sends it, and lanco is the long shafted one you hold or throw. Lancisto is a lancer, lanci is to spear something, and ĵetlanco is the javelin, which is where the word finally arrives in a modern stadium.