In French, we have what we call an accent circonflexe, which is usually sign of a former s that was erased during the evolution of French.
Modern French form: Forêt, hôpital, côte;
Older form: forestis, hospitalis, costa.
This is very interesting because in English we have a lot of those French-origin words but still with the s: forest, hospital, coast.
Some day, I was pondering the word guêpe (wasp), I tried to find by myself the old version of this word, guespe? guespa? guazpacho? I looked it up in the wonderful Antidote (French dictionary software) and I found that it actually comes from the Frankish word waspa, which comes from the Latin word vespa… wait what?! Waspa? Like, like wasp? How on Earth can guêpe and wasp
both have the same root? I was literally flabbergasted!
Ah English, you never stop surprising me!