Latin: Scrupulum, meaning a tiny stone (from Latin: scrupus sharp stone), indicates a weight of of a Roman ounce (i.e.) or, by extension, of other measures. Metaphorically, the stone is thought to be sharp and pricking, like a thorn.
The forms Latin: scripulum, Latin: scriptulum, Latin: scriplus and Latin: scriptulus can be found, Latin: scriptulum being also associated with the lines on a draughtboard.
French: Félix Gaffiot: Dictionnaire Illustré Latin Français, Hachette 1934