Why does it say ‘Pataca’?

Why does it say ‘Pataca’? I can't find that information

https://en.wikipedia.org/wiki/Pataca

Thank you. 
I can't find confirmation that 1 Pataco = 40 Réis.

It is alternative name listed in Standard catalogue of world coins.

1701-1800 6th edition gives following ratios for monetary system til 1825

20 Reis = 1 Vinten

100 Reis = 1 Tostao

480 Reis = 1 Cruzado

1600 Reis = Escudo

6400 Reis = 1 Peca

It does not list pataco in ratio table, but shows pataco name as alternative for 40 Reis on individual coins.

I assume Portuguese might have more insights on it.

Portuguese dictionaries says that pataco is “an old Portuguese bronze coin with value equal to two vinténs, forty réis or four centavos”

tokul

20 Reis = 1 Vinten

100 Reis = 1 Tostao

480 Reis = 1 Cruzado

1600 Reis = Escudo

6400 Reis = 1 Peca

Actual spelling in Portuguese: vintém, tostão and peça.