'Recipe!' is a Latin command — 'take!' Pharmacists were ordered to take ingredients; cooks borrowed the format.
A set of instructions for preparing a particular dish; a formula or method for achieving something.
From Latin 'recipe,' the second-person singular imperative of 'recipere' (to take back, to receive, to take again), composed of 're-' (back, again) + 'capere' (to take, to seize, to grasp), from PIE *keh₂p- (to grasp, to take). Medieval physicians wrote 'Recipe:' (abbreviated 'Rx' or '℞') at the head of a prescription as a directive to the pharmacist: 'Take the [following ingredients] and compound them.' The word migrated from pharmaceutical to culinary
The pharmaceutical abbreviation 'Rx' — still displayed on every pharmacy sign — is a stylized corruption of the Latin word 'recipe' (take!). The 'R' is from 'recipe' and the 'x' represents the slash through the leg of the 'R' that medieval scribes used as an abbreviation. So every 'Rx' symbol is a fossilized Latin imperative of the verb 'capere.'