English langage doesn’t exist … It is French badly pronounced : in this book whose title is quite provocative (that’s humour as the author say), Bernard Cerquiglini explain that English and French langage have had a common basis. I will give here some examples.
The book is quite technical so I did my best to simplify a few examples.

Coach has the same root as « cocher » that, in French, used to refer to a man driving a carriage drawn by horses. Both come from the French word « coche ».
Indeed, coach comes from a metaphore : the personal trainer being like the horses drawing the carriage (at least that’s what I undestood the author doesn’t explain exactly the metaphore).

Mail has the same root as « malle » in French (wich means a trunk).
They both comes from the word « malha » that used to refers to a leather bag. In English the word had specialized into the sense of « postal bag » and then, by metonymy has meant postal items (mail).

Spell has the same root (and same meaning ») as « épeler ». Both come from old French « espeler » itself coming from « spellon » (meaning to explain).

Shop has the same root as « échoppe » (in modern french, « boutique » is much more usual). Both word come from old French « eschoppe » itself coming from Dutch « schoppe ».

Chart with words derived from the same root :

French wordEnglish wordRoot
EspionSpyespie > espier > spehôn (=to observ)
Etage (floor/storey)Stageestage > ester > stare
NourriceNursenourrice>nourrir (raise in old French)