"Potable" and all related words hark back to one of the most debowdlerised Latin words used by that thirsty race. Here are some related Latin words from an online dictionary and their English definitions. You can tell that the meaning and content of the basic word
poto potare potavi potatum underwent expansion over time ...
potatio -onis f. [a drinking bout].
potio (1) -onis f. [drinking; a drink , a draught]; esp. [a love-draught, philtre].
poto potare potavi potatum and potum [to drink]; esp. [to drink heavily]; of things , [to absorb]. Hence partic. potus -a -um: pass. [drunk, drained]; act. [having drunk, drunken].
potor -oris m. [a drinker]; esp. [a tippler , drunkard].
potulentus (poculentus) -a -um [drinkable; drunk , intoxicated].
potus (1) -a -um partic. from poto; q.v.
potus (2) -us m. [a drinking , draught].
FWIW
- Pfranz
