reddere

Render comes from Old French rendre (to give back, to return), from Vulgar Latin *rendere, an alteration of Latin reddere (re- + dare, to give). The word entered English in the fourteenth century with multiple meanings: to give back, to submit, to translate, to make or cause to be. The cooking sense — to melt fat out of animal tissue by slow heating — is a specific application of the 'cause to be' meaning: rendering fat causes solid tissue to become liquid fat.

The technique is old. Before vegetable oils were widely available, animal fats — lard from pigs, tallow from cattle, schmaltz from chickens, dripping from roasts — were the primary cooking fats in Europe. Rendering was a household skill: you took the fatty trimmings, the suet, the skin, and heated them slowly until the fat melted out and the connective tissue turned crispy. The crispy remnants are called cracklings (in English), grattons (in French), or grieben (in Yiddish). Nothing was wasted.

Industrial rendering became a major industry in the nineteenth and twentieth centuries. Rendering plants process animal byproducts from slaughterhouses — hides, bones, fat, offal — into tallow (for soap, candles, and industrial lubricants), bone meal (for fertilizer), and protein meal (for animal feed). The word render, in industrial context, means processing the parts of the animal that cannot be sold as meat. The rendering industry is invisible and enormous: it processes roughly 60 billion pounds of raw material in the United States annually.

The word render also means to translate (rendering a text into another language) and to create a visual representation (rendering an architectural drawing). Each meaning involves transformation: fat becomes liquid, words become other words, ideas become images. The giving-back that the Latin root describes is always a transformation — you give the thing back in a different form than you received it.